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Vulnerability record · CVE-2026-5308 · published 22 May 2026

CVE-2026-5308: Mattermost server uncontrolled resource consumption vulnerability

Mattermost · Mattermost Server

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 enforce request body size limits on plugin HTTP endpoints which allows an attacker to cause a denial of service via crafted oversized HTTP requests.. Mattermost Advisory ID: MMSA-2026-00646

7.5 CVSS 3.1 High EPSS 0.45% · top 63.8% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score
0.45%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
23 Jul 2026Last modified by NVD

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 enforce request body size limits on plugin HTTP endpoints which allows an attacker to cause a denial of service via crafted oversized HTTP requests.. Mattermost Advisory ID: MMSA-2026-00646

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://mattermost.com/security-updates Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.9CVE-2026-4858Mattermost server path traversal vulnerabilityMattermost 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 check integration URL for path traversal which …EPSS 0.40%9.9CVE-2025-12421Mattermost server vulnerabilityMattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code…EPSS 0.35%9.9CVE-2025-12419Mattermost server vulnerabilityMattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during O…EPSS 0.35%9.9CVE-2025-4981Mattermost server uncontrolled search path element vulnerabilityMattermost versions 10.5.x <= 10.5.5, 9.11.x <= 9.11.15, 10.8.x <= 10.8.0, 10.7.x <= 10.7.2, 10.6.x <= 10.6.5 fail to sanitize filenames in the archi…EPSS 0.85%9.8CVE-2023-6458Mattermost server injection vulnerabilityMattermost webapp fails to validate route parameters in/<TEAM_NAME>/channels/<CHANNEL_NAME> allowing an attacker to perform a client-side path traver…EPSS 0.64%9.8CVE-2017-18908Mattermost server improper authentication vulnerabilityAn issue was discovered in Mattermost Server before 4.0.0, 3.10.2, and 3.9.2. A password-reset request was sometime sent to an attacker-provided e-ma…EPSS 1.2%9.8CVE-2017-18915Mattermost server incorrect default permissions vulnerabilityAn issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. After a restart of a server, an attacker might suddenly gain API Endpoin…EPSS 1.2%9.8CVE-2017-18920Mattermost server vulnerabilityAn issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.EPSS 1.2%

Source: NIST National Vulnerability Database (record CVE-2026-5308), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.