CVE-2026-24458
Published: 16 March 2026
Summary
CVE-2026-24458 is a high-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Mattermost Mattermost Server. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 19.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-7 (Unsuccessful Logon Attempts) and SC-5 (Denial-of-service Protection).
Deeper analysis
CVE-2026-24458 is a denial-of-service vulnerability in Mattermost versions 11.3.x up to and including 11.3.0, 11.2.x up to 11.2.2, and 10.11.x up to 10.11.10. The issue arises from the server's failure to properly handle very long passwords during login attempts, allowing multi-megabyte passwords to cause excessive CPU and memory consumption. Mapped to CWE-770 (Allocation of Resources Without Limits or Throttling), it carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and was published on 2026-03-16.
Unauthenticated attackers with network access can exploit this vulnerability by sending repeated login requests containing multi-megabyte passwords. Successful exploitation leads to server resource overload, resulting in degraded performance or complete denial of service without requiring privileges, user interaction, or authentication.
Mattermost Advisory MMSA-2026-00587 provides details on the issue, with further information available at https://mattermost.com/security-updates. Security practitioners should review this advisory for recommended patches and mitigation steps.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-12405
Vulnerability details
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct resource exhaustion DoS via unauthenticated exploitation of input handling flaw in public-facing server application (CWE-770).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-9 directly restricts the size and characteristics of password inputs during login to prevent resource exhaustion from multi-megabyte passwords.
SC-5 implements denial-of-service protections such as resource allocation controls and throttling to limit the impact of repeated large password login attempts.
AC-7 enforces limits on consecutive unsuccessful logon attempts, preventing attackers from repeatedly submitting oversized passwords to overload server CPU and memory.