Source: golang-1.27
Version: 1.27~rc2-1
Severity: grave
Tags: security upstream
X-Debbugs-Cc: carnil@debian.org, Debian Security Team <team@security.debian.org>
Control: clone -1 -2 -3
Control: reassign -2 src:golang-1.26 1.26.5-1
Control: retitle -2 golang-1.26: CVE-2026-33818 CVE-2026-56853 CVE-2026-56858 CVE-2026-56859 CVE-2026-56860 CVE-2026-56862 CVE-2026-56864 CVE-2026-56865
Control: reassign -3 src:golang-1.25 1.25.12-1
Control: retitle -3 golang-1.25: CVE-2026-33818 CVE-2026-56853 CVE-2026-56858 CVE-2026-56859 CVE-2026-56860 CVE-2026-56862 CVE-2026-56864 CVE-2026-56865

Hi,

The following vulnerabilities were published for go.

CVE-2026-33818[0]:
| Enforce a recursion limit in Unmarshal to prevent stack exhaustion
| when parsing deeply-nested, recursive structures.


CVE-2026-56853[1]:
| 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. ReadHeaderTimeout is unexpectedly not being
| applied when doing this.


CVE-2026-56858[2]:
| Previously, pathological inputs could close an unescaped '/' early,
| allowing for attack-controlled data to inject arbitrary content,
| potentially leading to XSS.


CVE-2026-56859[3]:
| Previously, DecodeElement would reset the depth counter causing it
| to never fire; this could lead to stack exhaustion.


CVE-2026-56860[4]:
| 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.


CVE-2026-56862[5]:
| Handshake messages, such as KeyUpdate, are always considered 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.


CVE-2026-56864[6]:
| 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


CVE-2026-56865[7]:
| 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


If you fix the vulnerabilities please also make sure to include the
CVE (Common Vulnerabilities & Exposures) ids in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-33818
https://www.cve.org/CVERecord?id=CVE-2026-33818
[1] https://security-tracker.debian.org/tracker/CVE-2026-56853
https://www.cve.org/CVERecord?id=CVE-2026-56853
[2] https://security-tracker.debian.org/tracker/CVE-2026-56858
https://www.cve.org/CVERecord?id=CVE-2026-56858
[3] https://security-tracker.debian.org/tracker/CVE-2026-56859
https://www.cve.org/CVERecord?id=CVE-2026-56859
[4] https://security-tracker.debian.org/tracker/CVE-2026-56860
https://www.cve.org/CVERecord?id=CVE-2026-56860
[5] https://security-tracker.debian.org/tracker/CVE-2026-56862
https://www.cve.org/CVERecord?id=CVE-2026-56862
[6] https://security-tracker.debian.org/tracker/CVE-2026-56864
https://www.cve.org/CVERecord?id=CVE-2026-56864
[7] https://security-tracker.debian.org/tracker/CVE-2026-56865
https://www.cve.org/CVERecord?id=CVE-2026-56865

Regards,
Salvatore

We believe that the bug you reported is fixed in the latest version of
golang-1.27, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1144340@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Dr. Tobias Quathamer <toddy@debian.org> (supplier of updated golang-1.27 package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sun, 16 Aug 2026 22:47:51 +0200
Source: golang-1.27
Architecture: source
Version: 1.27~rc3-1
Distribution: unstable
Urgency: medium
Maintainer: Debian Go Compiler Team <team+go-compiler@tracker.debian.org>
Changed-By: Dr. Tobias Quathamer <toddy@debian.org>
Closes: 1144340
Changes:
 golang-1.27 (1.27~rc3-1) unstable; urgency=medium
 .
   * New upstream version 1.27~rc3 (Closes: #1144340)
     - CVE-2026-56865
       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
     - CVE-2026-56864
       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
     - CVE-2026-56862
       Handshake messages, such as KeyUpdate, are always considered 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.
     - CVE-2026-56860
       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.
     - CVE-2026-56859
       Previously, DecodeElement would reset the depth counter causing it to
       never fire; this could lead to stack exhaustion.
     - CVE-2026-56858
       Previously, pathological inputs could close an unescaped '/' early,
       allowing for attack-controlled data to inject arbitrary content,
       potentially leading to XSS.
     - CVE-2026-56853
       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. ReadHeaderTimeout is unexpectedly not being applied when
       doing this.
     - CVE-2026-33818
       Enforce a recursion limit in Unmarshal to prevent stack exhaustion when
       parsing deeply-nested, recursive structures.
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