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Advisory record · GHSA-gqv7-j2j8-qmwq

Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation

CVSS 4.3 MediumEPSS 0.0019 · 8th percentile

Published by the GitHub Advisory Database at 16 Mar 2026, 15:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
github.com/mattermost/mattermost/server/v8Go<8.0.0-20260129133647-5d787969c2d58.0.0-20260129133647-5d787969c2d5
github.com/mattermost/mattermost-serverGo<5.3.2-0.20260129133647-5d787969c2d5 || >=10.11.0-rc1, <10.11.11 || >=11.2.0-rc1, <11.2.3 || >=11.3.0-rc1, <11.3.15.3.2-0.20260129133647-5d787969c2d5, 10.11.11, 11.2.3, 11.3.1
Identifiers
GHSA-gqv7-j2j8-qmwq · CVE-2026-2455 · GO-2026-4746
Weakness (CWE)
CWE-918
Tags
Published
16 Mar 2026
Updated
23 Mar 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Mattermost versions up to 10.11.10, 11.2.2 and 11.3.0 are affected. Because IPv4-mapped IPv6 addresses are not canonicalized before reserved IP validation, an attacker can perform server-side request forgery against internal services using such IPv6 literals. Upgrade to 10.11.11, 11.2.3, 11.3.1 or later.

Written 7 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
4.3 Medium 3.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N CNA (Mattermost)
  • CISA KEV Not listed.
  • EPSS 0.0019, the 8th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 15:08 UTC First seen by agentprime
  2. 31 Oct 2026, 15:08 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.