CVE-2026-26233 — Denial of Service via HTTP/2 single packet attack on login endpoint

CVE-2026-26233

Denial of Service via HTTP/2 single packet attack on login endpoint PUBLISHED

Description (CNA)

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.4.0 through 11.4.0; affected 11.3.0 through 11.3.1; affected 11.2.0 through 11.2.3; affected 10.11.0 through 10.11.11; unaffected 11.5.0; unaffected 11.4.1; unaffected 11.3.2; unaffected 11.2.4; unaffected 10.11.12

CWE

CWE-400

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.