Medium severity4.3NVD Advisory· Published Mar 16, 2026· Updated Jun 17, 2026
CVE-2026-25783
CVE-2026-25783
Description
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
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/mattermost/mattermost/server/v8Go | < 8.0.0-20260129181235-1346cf529aef | 8.0.0-20260129181235-1346cf529aef |
github.com/mattermost/mattermost-serverGo | < 5.3.2-0.20260129181235-1346cf529aef | 5.3.2-0.20260129181235-1346cf529aef |
github.com/mattermost/mattermost-serverGo | >= 10.11.0-rc1, < 10.11.11 | 10.11.11 |
github.com/mattermost/mattermost-serverGo | >= 11.2.0-rc1, < 11.2.3 | 11.2.3 |
github.com/mattermost/mattermost-serverGo | >= 11.3.0-rc1, < 11.3.1 | 11.3.1 |
Affected products
6- osv-coords4 versionspkg:rpm/opensuse/govulncheck-vulndb&distro=openSUSE%20Leap%2015.6pkg:golang/github.com/mattermost/mattermost/server/v8pkg:golang/github.com/mattermost/mattermost-serverpkg:rpm/opensuse/govulncheck-vulndb&distro=openSUSE%20Leap%2016.0
< 0.0.20260326T203309-150000.1.155.2+ 3 more
- (no CPE)range: < 0.0.20260326T203309-150000.1.155.2
- (no CPE)range: < 8.0.0-20260129181235-1346cf529aef
- (no CPE)range: < 5.3.2-0.20260129181235-1346cf529aef
- (no CPE)range: < 0.0.20260723T184607-160000.1.1
11.3.0+ 1 more
- (no CPE)range: 11.3.0
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*range: >=10.11.0,<10.11.11
Patches
Vulnerability mechanics
References
4- github.com/advisories/GHSA-2v3w-6g35-5f9vghsaADVISORY
- mattermost.com/security-updatesnvdVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-25783ghsaADVISORY
- github.com/mattermost/mattermost/commit/1346cf529aef0672c39a56ec10d1b8a9c8fb387dghsaWEB
News mentions
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