CVE-2026-4053: Mattermost doesn't enforce the PostEditTimeLimit on non-message post fields

May 15, 2026 (updated May 28, 2026)

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce the PostEditTimeLimit on non-message post fields which allows an authenticated user to modify post file attachments, props, and pin status after the edit window has expired via the post patch and update API endpoints. Mattermost Advisory ID: MMSA-2026-00631.

References

github.com/advisories/GHSA-hw87-6jcq-9f8q
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-4053

Code Behaviors & Features

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