GHSA-2v3w-6g35-5f9v

ghsaUSosv

Mattermost fails to properly validate User-Agent header tokens

view advisory published 2026-03-16Licence: CC-BY-4.0

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Mattermost Advisory ID: MMSA-2026-00586

describes (1)

Related CVEs.

ID	severity	EPSS	exploitable	published
CVE-2026-25783US	—	0.30% (22nd)	—	2026-03-16
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a req…

references

External citations — patches, advisories, analysis.

https://github.com/mattermost/mattermostPACKAGE
https://github.com/mattermost/mattermost/commit/1346cf529aef0672c39a56ec10d1b8a9c8fb387dWEB
https://mattermost.com/security-updatesWEB
https://nvd.nist.gov/vuln/detail/CVE-2026-25783ADVISORY

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