DDoS via Login RateLimit Bypass in Mattermost 10.1111.4 (CVE202626233)
CVE-2026-26233 Published on March 25, 2026
Denial of Service via HTTP/2 single packet attack on login endpoint
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
Vulnerability Analysis
CVE-2026-26233 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-26233 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-26233
Want to know whenever a new CVE is published for MatterMost? stack.watch will email you.
Affected Versions
Mattermost:- Version 11.4.0, <= 11.4.0 is affected.
- Version 11.3.0, <= 11.3.1 is affected.
- Version 11.2.0, <= 11.2.3 is affected.
- Version 10.11.0, <= 10.11.11 is affected.
- Version 11.5.0 is unaffected.
- Version 11.4.1 is unaffected.
- Version 11.3.2 is unaffected.
- Version 11.2.4 is unaffected.
- Version 10.11.12 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.