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Advisory record · GHSA-ph22-fw5m-w2q9

Mattermost allows attackers to spoof permalink embeds

CVSS 4.3 MediumEPSS 0.0012 · 1st 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<8.0.0-20260123211116-9efe617be8b88.0.0-20260123211116-9efe617be8b8
github.com/mattermost/mattermost-serverGo<5.3.2-0.20260123211116-9efe617be8b8 || >=10.11.0-rc1, <10.11.11 || >=11.2.0-rc1, <11.2.3 || >=11.3.0-rc1, <11.3.15.3.2-0.20260123211116-9efe617be8b8, 10.11.11, 11.2.3, 11.3.1
Identifiers
GHSA-ph22-fw5m-w2q9 · CVE-2026-2457 · GO-2026-4732
Weakness (CWE)
CWE-346
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 11.3.0 and earlier, 11.2.x through 11.2.2, and 10.11.x through 10.11.10 fail to sanitize client-supplied post metadata. An authenticated attacker can use crafted post update requests to spoof permalink embeds that impersonate other users. Upgrade to 10.11.11, 11.2.3, or 11.3.1, matching your release line.

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:N/I:L/A:N CNA (Mattermost)
  • CISA KEV Not listed.
  • EPSS 0.0012, the 1st percentile, on 11 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.