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 t…

Code

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No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

1. Mar 16, 2026 · NIST NVD

   Detected

   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

2. Jun 17, 2026 · NIST NVD

   Updated

   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

Affected

• cpe mattermost/mattermost serverversion unspecified

Sources

• CVE.orgVulnerability recordCVE-2026-25783

  Official CVE identifier

  cve.org
• NIST NVDVulnerability recordCVE-2026-25783

  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

  nvd.nist.gov

References

• Vendor Advisory · mattermost.com