This release includes a fix to address a breakage affecting unencrypted
HTTP/2 (h2c) connections caused by a security patch included in last
patch release.
See go.dev/issue/80876 for details.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
This release includes 10 security fixes following the security policy:
- x/mod/sumdb/tlog: fix transparency log tile verification bypass
A malicious GOPROXY was previously capable of forging
up to two sumdb tiles that allow for a requested module
to bypass the GOSUMDB check and persist attacker-controlled
module content to a local Go module cache.
This attack allows for a malicious GOPROXY to serve
malicious module content that cannot be detected
by evaluating the transparency log.
All tiles are now correctly verified against their parents.
In order to determine if you have been affected:
rm -r go.sum go.work.sum vendor/ && go mod tidy
Thanks to Filippo Valsorda (Geomys) for reporting this issue.
This is CVE-2026-56865 and Go issue https://go.dev/issue/80744.
- x/mod/sumdb: ignore unrelated, unauthenticated hashes in Lookup
A malicious GOSUMDB was capable of serving arbitrary
module content not contained within the transparency
log.
This attack allows for a coordinating GOPROXY and
GOSUMDB to serve a client malicious module content
that cannot be detected by evaluating the transparency
log.
In order to determine if you have been affected:
rm -r go.sum go.work.sum vendor/ && go mod tidy
Thanks to mundur for reporting this issue.
This is CVE-2026-56864 and Go issue https://go.dev/issue/80745.
- encoding/xml: add recursion depth guard during decode
Previously, DecodeElement would reset the depth counter
causing it to never fire; this could lead to stack
exhaustion.
This is CVE-2026-56859 and Go issue https://go.dev/issue/80481.
net/http: apply ReadHeaderTimeout when doing unencrypted HTTP/2 check
When a server is configured to support unencrypted HTTP/2, it reads a
few bytes from each new connection to see if they contain the HTTP/2
client preface. Previously, this was being done with no timeout applied.
ReadHeaderTimeout is now applied for this.
This is CVE-2026-56853 and Go issue https://go.dev/issue/80205.
- net/url: avoid quadratic complexity in resolvePath
Previously, resolving relative paths containing parent directory (..) segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead.
Now, path resolution operates on a byte buffer using index-based backtracking for .. segments, eliminating the quadratic time complexity and significantly reducing memory allocations.
This is CVE-2026-56860 and Go issue https://go.dev/issue/80494.
- golang.org/x/net/dns/dnsmessage: panic when parsing invalid SVCB record
Parsing an invalid SVCB or HTTPS RR can panic when
the size of a parameter value overflows the message buffer.
Thanks to Mundur (https://github.com/M0nd0R) for reporting this issue.
This is CVE-2026-46600 and Go issue https://go.dev/issue/79795.
- crypto/tls: limit handshake messages we are willing to accept post-handshake
Previously, we always counted handshake messages, such as KeyUpdate, as
state-advancing, regardless of whether a handshake has been completed or
not. As a result, a malicious client can keep sending KeyUpdate messages
to force the server to keep performing key derivation operations
indefinitely.
Thanks to Qi Deng of Aurascape.ai for reporting this issue.
This is CVE-2026-56862 and Go issue https://go.dev/issue/80528.
- html/template: fix Javascript regexp context tracking
Previously, pathological inputs could close an
unescaped / early, allowing for attack-controlled
data to inject arbitrary content, potentially
leading to XSS.
Thanks to Ali Sherif for reporting this issue.
This is CVE-2026-56858 and Go issue https://go.dev/issue/80435.
- x/net/idna: failure to reject ASCII-only Punycode-encoded labels
The ToASCII and ToUnicode functions incorrectly accepted Punycode-encoded labels
that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com")
incorrectly returned the name "example.com" rather than an error.
The idna package implements the processing algorithm from UTS 46.
Older versions of UTS 46 included a specification bug which permitted
multiple ASCII labels to decode to the same Unicode label.
UTS 46 revision 33 fixed the specification bug.
The idna package now implements the updated specification.
This behavior can lead to privilege escalation in programs using the idna package.
For example, a program which performs privilege checks on the ASCII hostname
may reject "example.com" but permit "xn--example-.com". If that program subsequently
converts the ASCII hostname to Unicode, it will inadvertently permits access
to the Unicode name "example.com".
Thanks to KC1zs4 (https://github.com/KC1zs4) for reporting this issue.
This is CVE-2026-39821 and Go issue https://go.dev/issue/78760.
- encoding/asn1: enforce maximum recursion depth
Enforce a recursion limit in Unmarshal to prevent stack exhaustion
when parsing deeply-nested, recursive structures.
Thanks to Marwan Atia (marwans...@gmail.com) for reporting this issue.
This is CVE-2026-33818 and Go issue https://go.dev/issue/80405.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
go1.26.5 (released 2026-07-07) includes security fixes to the crypto/tls
and os packages, as well as bug fixes to the compiler, the runtime, the
go command, and the net, os, and syscall packages. See the Go 1.26.5
milestone on our issue tracker for details;
- https://github.com/golang/go/issues?q=milestone%3AGo1.26.5+label%3ACherryPickApproved
- full diff: https://github.com/golang/go/compare/go1.26.4...go1.26.5
From the security announcement:
We have just released Go versions 1.26.5 and 1.25.12, minor point releases.
These releases include 2 security fixes following the security policy:
- os: Root escape via symlink plus trailing slash
On Unix systems, opening a file in an os.Root improperly
followed symlinks to locations outside of the Root when
the final path component of the a path is a symbolic link
and the path ends in /.
For example, root.Open("symlink/") would open "symlink"
even when "symlink" is a symbolic link pointing outside of the root.
On Unix, openat(fd, path, O_NOFOLLOW) will follow symlinks
in path when path ends in a /. Root failed to account for
this behavior, permitting paths with a trailing / to escape.
It now properly sanitizes the path parameter provided to openat.
hanks to Mundur for reporting this issue.
This is CVE-2026-39822 and Go issue https://go.dev/issue/79005.
- crypto/tls: Encrypted Client Hello privacy leak
he Encrypted Client Hello implementation would leak the pre-shared key
dentities during the handshake, allowing a passive network observer who can
ollect handshakes to de-anonymize the hostname of the server, even when ECH was
eing used.
Thanks to Coia Prant (github.com/rbqvq) for reporting this issue.
This is CVE-2026-42505 and Go issue https://go.dev/issue/79282.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This release include 3 security fixes following the security policy:
- mime: quadratic complexity in WordDecoder.DecodeHeader
Decoding a maliciously-crafted MIME header containing many invalid
encoded-words could consume excessive CPU.
The MIME decoder now better handles this case.
Thanks to p4p3r (https://hackerone.com/p4p3r_hak) for reporting this issue.
This is CVE-2026-42504 and Go issue https://go.dev/issue/79217.
- net/textproto: arbitrary input are included in errors without any escaping
When returning errors, functions in the net/textproto package would
include its input as part of the error, without any escaping. Note that
said input is often controlled by external parties when using this
package naturally. For example, a net/http client uses ReadMIMEHeader
when parsing the headers it receive from a server.
As a result, an attacker could inject arbitrary content into the error.
Practically, this can result in an attacker injecting misleading
content, terminal control bytes, etc. into a victim's output or logs.
This is CVE-2026-42507 and Go issue https://go.dev/issue/79346
- crypto/x509: split candidate hostname only once
(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop
over all DNS Subject Alternative Name (SAN) entries. This caused
strings.Split(host, ".") to execute repeatedly on the same input hostname.
With a large DNS SAN list, verification costs scaled quadratically based on the
number of SAN entries multiplied by the hostname's label count. Because
x509.Verify validates hostnames before building the certificate chain, this
overhead occurred even for untrusted certificates.
Thanks to Jakub Ciolek (https://ciolek.dev) for reporting this issue.
This is CVE-2026-27145 and https://go.dev/issue/79694.
View the release notes for more information:
https://go.dev/doc/devel/release#go1.26.4
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
This makes it easier to verify the sha matches the tag, and may help
with dependabot not updating the version-comment correctly.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This release include 11 security fixes:
- cmd/go: malicious module proxy can bypass checksum database
A malicious module proxy could exploit a flaw in the go command's
validation of module checksums to bypass checksum database validation.
This vulnerability affects any user using an untrusted module proxy
(GOMODPROXY) or checksum database (GOSUMDB).
A malicious module proxy can serve altered versions of the Go toolchain.
When selecting a different version of the Go toolchain than the
currently installed toolchain (due to the GOTOOLCHAIN environment variable,
or a go.work or go.mod with a toolchain line), the go command will download
and execute a toolchain provided by the module proxy. A malicious module
proxy can bypass checksum database validation for this downloaded
toolchain.
Since this vulnerability affects the security of toolchain downloads,
setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade
your base Go toolchain.
The go tool always validates the hash of a toolchain before executing it,
so fixed versions will refuse to execute any cached, altered versions of the
toolchain.
The go tool trusts go.sum files to contain accurate hashes of the current
module's dependencies. A malicious proxy exploiting this vulnerability to
serve an altered module will have caused an incorrect hash to be recorded
in the go.sum. Users who have configured a non-trusted GOPROXY can determine
if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify",
which will revalidate all dependencies of the current module.
The specific flaw in more detail:
The go command consults the checksum database to validate downloaded modules,
when a module is not listed in the go.sum file. It verifies that the module hash
reported by the checksum database matches the hash of the downloaded module.
If, however, the checksum database returns a successful response that contains
no entry for the module, the go command incorrectly permitted validation to succeed.
A module proxy may mirror or proxy the checksum database, in which case the go
command will not connect to the checksum database directly. Checksums reported
by the checksum database are cryptographically signed, so a malicious proxy
cannot alter the reported checksum for a module. However, a proxy which returns
an empty checksum response, or a checksum response for an unrelated module,
could cause the go command to proceed as if a downloaded module has been validated.
The go command now properly checks checksum database responses to ensure
that the expected module signature is present, not just that if a signature is
present it matches the expectation.
Thanks to Mundur (https://github.com/M0nd0R) for reporting this issue.
This is CVE-2026-42501 and Go issue https://go.dev/issue/79070.
- net/http/httputil: ReverseProxy forwards queries with more than urlmaxqueryparams parameters
When used with a Rewrite function, or a Director function which parses query parameters,
ReverseProxy sanitizes the forwarded request to remove query parameters which are not
parsed by url.ParseQuery. ReverseProxy did not take ParseQuery's limit on the total number
of query parameters (controlled by GODEBUG=urlmaxqueryparams=N) into account.
This could permit ReverseProxy to forward a request containing a query parameter
that was not visible to the Rewrite function.
For example, the query "a1=x&a2=x&...&a10000=x&hidden=y" could forward the parameter
"hidden=y" while hiding it from the proxy's Rewrite function.
ReverseProxy now avoids forwarding parameters that exceed the ParseQuery limit.
This is CVE-2026-39825 and Go issue https://go.dev/issue/78948.
- net: panic in Dial and LookupPort when handling NUL byte on Windows
The Dial and LookupPort functions would panic on Windows when provided
with an input containing a NUL (0). These functions now return an error
rather than panicking.
This is CVE-2026-39836 and Go issue https://go.dev/issue/79006.
- net/mail: quadratic string concatenation in consumePhrase
Pathological inputs could cause DoS through consumePhrase
when parsing an email address according to RFC 5322.
This is CVE-2026-42499 and Go issue https://go.dev/issue/78987.
- net/mail: quadratic string concatentation in consumeComment
Well-crafted inputs reaching ParseAddress, ParseAddressList,
and ParseDate were able to trigger excessive CPU exhaustion
and memory allocations.
This is CVE-2026-39820 and Go issue https://go.dev/issue/78566.
- cmd/go: "go bug" follows symlinks in predictable temporary filenames
The "go bug" command wrote to two files with predictable names in
the system temporary directory (for example, "/tmp").
An attacker with access to the temporary directory could create a
symlink in one of these names, causing "go bug" to overwrite the
target of the symlink.
The "go bug" command now uses os.MkdirTemp to create a safe
working directory.
Thanks to Harshit Gupta (Mr HAX) for reporting this issue.
This is CVE-2026-39819 and Go issue https://go.dev/issue/78584.
- cmd/go: "go tool pack" does not sanitize output paths
The "go tool pack" subcommand is a minimal version of the Unix ar utility.
It is used by the compiler as an internal tool with known-good inputs.
The "pack" subcommand did not sanitize output filenames.
When invoked to extract a malicious archive file, it could write
files to arbitrary locations on the filesystem.
The "pack" subcommand now refuses to extract files with names
containing any directory components.
Thanks to Harshit Gupta (Mr HAX) for reporting this issue.
This is CVE-2026-39817 and Go issue https://go.dev/issue/78778.
- net/http: infinite loop in HTTP/2 transport when given bad SETTINGS_MAX_FRAME_SIZE
When processing HTTP/2 SETTINGS frames, transport will enter an infinite loop of
writing CONTINUATION frames if it receives a SETTINGS_MAX_FRAME_SIZE with a
value of 0.
This allows potential DoS against a client by a malicious server. HTTP/2
transport now properly checks that the received SETTINGS_MAX_FRAME_SIZE is
valid.
Thanks to Marwan Atia (marwansamir688@gmail.com) for reporting this issue.
This is CVE-2026-33814 and Go issue https://go.dev/issue/78476.
- html/template: escaper bypass leads to XSS
If a trusted template author were to write a
tag containing an empty type attribute or a type
attribute with an ASCII whitespace, the execution of
the template would incorrectly escape any data passed
into the block.
Thanks to Mundur (https://github.com/M0nd0R) for reporting this issue.
This is CVE-2026-39826 and Go issue https://go.dev/issue/78981.
- net: crash when handling long CNAME response
When using LookupCNAME with the cgo DNS resolver,
a very long CNAME response could trigger a double-free of C memory
and a crash. The double-free has been fixed.
Thanks to hamayanhamayan for reporting this issue.
This is CVE-2026-33811 and Go issue https://go.dev/issue/78803.
- html/template: bypass of meta content URL escaping causes XSS
CVE-2026-27142 fixed a vulnerability in which URLs were not
correctly escaped inside of a tag's attribute.
If the URL content were to insert ASCII whitespaces around the
= rune inside of the attribute, the escaper would
fail to similarly escape it, leading to XSS.
Dynamic inputs to a tag's attribute are now
whitespace sanitized prior to escaping.
Thanks to Samy Ghannad for reporting this issue.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
go1.26.2 (released 2026-04-07) includes security fixes to the go command,
the compiler, and the archive/tar, crypto/tls, crypto/x509, html/template,
and os packages, as well as bug fixes to the go command, the go fix command,
the compiler, the linker, the runtime, and the net, net/http, and net/url
packages. See the Go 1.26.2 milestone on our issue tracker for details;
- https://github.com/golang/go/issues?q=milestone%3AGo1.26.2+label%3ACherryPickApproved
- full diff: https://github.com/golang/go/compare/go1.26.1...go1.26.2
From the security announce:
We have just released Go versions 1.26.2 and 1.25.9, minor point releases.
These releases include 10 security fixes following the security policy:
- os: Root.Chmod can follow symlinks out of the root on Linux
On Linux, if the target of Root.Chmod is replaced with a symlink while
the chmod operation is in progress, Chmod could operate on the target
of the symlink, even when the target lies outside the root.
The Linux fchmodat syscall silently ignores the AT_SYMLINK_NOFOLLOW flag,
which Root.Chmod uses to avoid symlink traversal. Root.Chmod checks its
target before acting and returns an error if the target is a symlink
lying outside the root, so the impact is limited to cases where the
target is replaced with a symlink between the check and operation.
On Linux, Root.Chmod now uses the fchmodat2 syscall when available, and
an workaround using /proc/self/fd otherwise.
Thanks to Uuganbayar Lkhamsuren for reporting this issue.
This is CVE-2026-32282 and Go issue https://go.dev/issue/78293.
- html/template: JS template literal context incorrectly tracked
Context was not properly tracked across template branches for JS template
literals, leading to possibly incorrect escaping of content when branches were
used.
Additionally template actions within JS template literals did not properly
track
the brace depth, leading to incorrect escaping being applied.
These issues could cause actions within JS template literals to be incorrectly
or improperly escaped, leading to XSS vulnerabilities.
This only affects templates that use template actions within JS template
literals.
This is CVE-2026-32289 and Go issue https://go.dev/issue/78331.
- crypto/x509: excluded DNS constraints not properly applied to wildcard domains
When verifying a certificate chain containing excluded DNS constraints, these
constraints are not correctly applied to wildcard DNS SANs which use a
different
case than the constraint.
For example, if a certificate contains the DNS name "*.example.com" and the
excluded DNS name "EXAMPLE.COM", the constraint will not be applied.
This only affects validation of otherwise trusted certificate chains, issued
by
a root CA in the VerifyOptions.Roots CertPool, or in the system certificate
pool.
This issue only affects Go 1.26.
Thank you to Riyas from Saintgits College of Engineering, k1rnt, @1seal for
reporting this issue.
This is CVE-2026-33810 and Go issue https://go.dev/issue/78332.
- cmd/compile: no-op interface conversion bypasses overlap checking
Previously, the compiler failed to unwrap pointers contained within
a no-op interface conversion leading to an incorrect determination
of a non-overlapping move.
To prevent unsafe move operations, the compiler will now unwrap all
such conversions before considering a move non-overlapping.
Thank you to Jakub Ciolek - https://ciolek.dev/ for reporting this issue.
This is CVE-2026-27144 and Go issue https://go.dev/issue/78371.
- cmd/compile: possible memory corruption after bound check elimination
Previously, slices and arrays accessed using induction variables
were sometimes incorrectly proved in-bound. If the induction variable
used for indexing were to overflow or underflow, it could allow access
to memory beyond the scope of the original slice or array.
To prevent this behavior, the compiler ensures that any mutated induction
variable that overflows/underflows with respect to its loop condition
is not used for bound check elimination.
Thank you to Jakub Ciolek - https://ciolek.dev/ for reporting this issue.
This is CVE-2026-27143 and Go issue https://go.dev/issue/78333.
- archive/tar: unbounded allocation when parsing old format GNU sparse map
tar.Reader could allocate an unbounded amount of memory when reading
a maliciously-crafted archive containing a large number of sparse
regions encoded in the "old GNU sparse map" format.
We now limit both the number of old GNU sparse map extension blocks,
and the total number of sparse file entries, regardless of encoding.
Thanks to Colin Walters (wal...@verbum.org) who initially reported this issue.
Thanks also to Uuganbayar Lkhamsuren (https://github.com/uug4na) and Jakub
Ciolek
who additionally reported this issue.
This is CVE-2026-32288 and Go issue https://go.dev/issue/78301.
- crypto/tls: multiple key update handshake messages can cause connection to
deadlock
If one side of the TLS connection sends multiple key update messages
post-handshake in a single record, the connection can deadlock, causing
uncontrolled consumption of resources. This can lead to a denial of service.
This only affects TLS 1.3.
Thank you to Jakub Ciolek - https://ciolek.dev/ for reporting this issue.
This is CVE-2026-32283 and Go issue https://go.dev/issue/78334.
- cmd/go: trust layer bypass when using cgo and SWIG
A well-crafted SWIG source file could take advantage
of a file-naming convention used inside the trust
boundary of the cgo compiler. Doing so could result
in arbitrary code execution during build time.
SWIG files are disallowed from using this convention.
Thank you to Juho Forsén of Mattermost for reporting this issue.
This is CVE-2026-27140 and Go issue https://go.dev/issue/78335.
- crypto/x509: unexpected work during chain building
During chain building, the amount of work that is done is not correctly
limited
when a large number of intermediate certificates are passed in
VerifyOptions.Intermediates, which can lead to a denial of service. This
affects
both direct users of crypto/x509 and users of crypto/tls.
Thank you to Jakub Ciolek - https://ciolek.dev/ for reporting this issue.
This is CVE-2026-32280 and Go issue https://go.dev/issue/78282.
- crypto/x509: inefficient policy validation
Validating certificate chains which use policies is unexpectedly inefficient
when certificates in the chain contain a very large number of policy mappings,
possibly causing denial of service.
This only affects validation of otherwise trusted certificate chains, issued
by
a root CA in the VerifyOptions.Roots CertPool, or in the system certificate
pool.
Thank you to Jakub Ciolek - https://ciolek.dev/ for reporting this issue.
This is CVE-2026-32281 and Go issue https://go.dev/issue/78281.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
- gha runners updated to ubuntu 22.04
- e2e now runs against moby 23.0, 24.0 and 25.0
- temporarily skip broken test for moby < 25
Signed-off-by: Christopher Petito <chrisjpetito@gmail.com>
Paweł Gronowski
Sebastiaan van Stijn
Sebastiaan van StijnandGitHub
dependabot[bot]andGitHub
CrazyMax
Christopher Petito
David Karlsson