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High severity7.5NVD Advisory· Published May 22, 2026· Updated May 22, 2026

CVE-2026-5740

CVE-2026-5740

Description

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

2
  • Mattermost/Mattermost2 versions
    cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*+ 1 more
    • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*range: >=10.11.0,<10.11.15
    • (no CPE)range: (11.4.x <= 11.4.4) || (11.5.x <= 11.5.3) || (11.6.x <= 11.6.0) || (10.11.x <= 10.11.14)

Patches

Vulnerability mechanics

References

1

News mentions

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