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Servers and applications

CVE-2026-93849

Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames

Severity
Medium 6.5
Published
26 Oct 2026
Last changed
2 Nov 2026
Added to UpHeron
3 Nov 2026
Fixed in
11.7.11, 11.8.6, 11.9.2, 11.10.2
Sources
NVD, CVE Program

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..…

Affected software

SoftwareAffected versions
MattermostServers and applications · cna:mattermost|mattermost
  • From 11.7.0 up to 11.7.10
  • From 11.8.0 up to 11.8.5
  • From 11.9.0 up to 11.9.1
  • From 11.10.0 up to 11.10.1
MattermostServers and applications · cpe:a:mattermost:mattermost_server
  • From 11.7.0 before 11.7.11
  • From 11.8.0 before 11.8.6
  • From 11.9.0 before 11.9.2
  • From 11.10.0 before 11.10.2

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2026-93849
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2026-93849