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.
release notes: https://go.dev/doc/devel/release#go1.26.6
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
Vagrant is no longer well maintained: e.g., its apt repository does not
provide packages for Ubuntu 26.04 (hashicorp/vagrant#13811), and recent
Fedora boxes are no longer published to HashiCorp's registry, so the CI
had to download the box file manually from Fedora mirrors.
The test scripts in the Vagrantfile were split out to script/vm/*.sh .
The scripts depend on neither Vagrant nor Lima, and can be used with
other VM environments too.
Assisted-by: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
(cherry picked from commit a42b09aaa6)
(cherry-pick was not clean)
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Paweł Gronowski