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VulnerabilityPublished

CVE-2026-93849: Mattermost · Excessive Memory Allocation

Affects MattermostSource CVE Database V5

0

Not known to be exploited · CVSS 6.5 Medium.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
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 26 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: 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 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
MattermostMattermostAffected
  • >=11.9.0 <=11.9.1
  • >=11.8.0 <=11.8.5
  • >=11.7.0 <=11.7.10
  • >=11.10.0 <=11.10.1
Fixed in–

AI-suggested

Until a fix is available, restrict access to Mattermost WebSocket endpoints to trusted users only and monitor for unusual memory usage patterns. Avoid exposing Mattermost WebSocket services to untrusted networks. Follow vendor advisories for updates.

Description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768

References

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