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VulnerabilityPublished

CVE-2026-16251: Mattermost · Unthrottled Resource Allocation

Affects MattermostSource GCVE Database

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Not known to be exploited · CVSS 6.5 Medium.

Data as of 29 Oct 2026, 22:01 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Mattermost)CVSS 3.16.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 16 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Mattermost MattermostAffected
  • 11.7.0 – 11.10.0
4 affected builds
Fixed in–

AI-suggested

Until a fix is available, consider limiting exposure of the image proxy feature or applying resource usage limits at the infrastructure level to mitigate potential memory exhaustion.

Description

CVE-2026-16251 is a vulnerability in Mattermost versions 11.7.0, 11.8.0, 11.9.0, and 11.10.0 where the application fails to limit the size of remote image responses buffered in memory during local image proxy direct fetches. This flaw allows a remote attacker to cause memory exhaustion on the server by sending a crafted oversized image response.

References

Community reviews

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