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>
update contributing guide link and improve PR template formatting in `.github/PULL_REQUEST_TEMPLATE.md`
Signed-off-by: Paulchen <lukas.23022005@gmail.com>
Signed-off-by: Lukas Michael <lukas.23022005@gmail.com>
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>
Ensure PRs have a milestone set and that it matches the next release
version declared in the root VERSION file.
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>
go1.25.8 (released 2026-03-05) includes security fixes to the html/template,
net/url, and os packages, as well as bug fixes to the go command, the compiler,
and the os package. See the Go 1.25.8 milestone on our issue tracker for details.
- 1.25.8 https://github.com/golang/go/issues?q=milestone%3AGo1.25.8+label%3ACherryPickApproved
- diff: https://github.com/golang/go/compare/go1.25.7...go1.25.8
- 1.26.1 https://github.com/golang/go/issues?q=milestone%3AGo1.26.1+label%3ACherryPickApproved
- diff: https://github.com/golang/go/compare/go1.26.0...go1.26.1
---
We have just released Go versions 1.26.1 and 1.25.8, minor point releases.
These releases include 5 security fixes following the security policy:
crypto/x509: incorrect enforcement of email constraints
- When verifying a certificate chain which contains a certificate containing
multiple email address constraints (composed of the full email address) which
share common local portions (the portion of the address before the '@'
character) but different domain portions (the portion of the address after the
'@' character), these constraints will not be properly applied, and only the
last constraint will be considered.
This can allow certificates in the chain containing email addresses which are
either not permitted or excluded by the relevant constraints to be returned by
calls to Certificate.Verify. Since the name constraint checks happen after chain
building is complete, this only applies to certificate chains which chain to
trusted roots (root certificates either in VerifyOptions.Roots or in the system
root certificate pool), requiring a trusted CA to issue certificates containing
either not permitted or excluded email addresses.
This issue only affects Go 1.26.
Thanks to Jakub Ciolek for reporting this issue.
This is CVE-2026-27137 and Go issue https://go.dev/issue/77952.
- crypto/x509: panic in name constraint checking for malformed certificates
Certificate verification can panic when a certificate in the chain has an empty
DNS name and another certificate in the chain has excluded name constraints.
This can crash programs that are either directly verifying X.509 certificate
chains, or those that use TLS.
Since the name constraint checks happen after chain building is complete, this
only applies to certificate chains which chain to trusted roots (root
certificates either in VerifyOptions.Roots or in the system root certificate
pool), requiring a trusted CA to issue certificates containing malformed DNS
names.
This issue only affects Go 1.26.
Thanks to Jakub Ciolek for reporting this issue.
This is CVE-2026-27138 and Go issue https://go.dev/issue/77953.
- html/template: URLs in meta content attribute actions are not escaped
Actions which insert URLs into the content attribute of HTML meta tags are not
escaped. This can allow XSS if the meta tag also has an http-equiv attribute
with the value "refresh".
A new GODEBUG setting has been added, htmlmetacontenturlescape, which can be
used to disable escaping URLs in actions in the meta content attribute which
follow "url=" by setting htmlmetacontenturlescape=0.
This is CVE-2026-27142 and Go issue https://go.dev/issue/77954.
- net/url: reject IPv6 literal not at start of host
The Go standard library function net/url.Parse insufficiently
validated the host/authority component and accepted some invalid URLs
by effectively treating garbage before an IP-literal as ignorable.
The function should have rejected this as invalid.
To prevent this behavior, net/url.Parse now rejects IPv6 literals
that do not appear at the start of the host subcomponent of a URL.
Thanks to Masaki Hara (https://github.com/qnighy) of Wantedly.
This is CVE-2026-25679 and Go issue https://go.dev/issue/77578.
- os: FileInfo can escape from a Root
On Unix platforms, when listing the contents of a directory using
File.ReadDir or File.Readdir the returned FileInfo could reference
a file outside of the Root in which the File was opened.
The contents of the FileInfo were populated using the lstat system
call, which takes the path to the file as a parameter. If a component
of the full path of the file described by the FileInfo is replaced with
a symbolic link, the target of the lstat can be directed to another
location on the filesystem.
The impact of this escape is limited to reading metadata provided by
lstat from arbitrary locations on the filesystem. This could be used
to probe for the presence or absence of files as well as gleaning
metadata like file sizes, but does not permit reading or writing files
outside the root.
The FileInfo is now populated using fstatat.
Thank you to Miloslav Trmač of Red Hat for reporting this issue.
This is CVE-2026-27139 and Go issue https://go.dev/issue/77827.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
