https://groups.google.com/g/golang-announce/c/EdhZqrQ98hk announces:
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.
View the release notes for more information:
https://go.dev/doc/devel/release#go1.26.1
You can download binary and source distributions from the Go website:
https://go.dev/dl/
To compile from source using a Git clone, update to the release with
git checkout go1.26.1 and build as usual.
Thanks to everyone who contributed to the releases.
Cheers,
Cherry and David for the Go team
