Skip to main content

Boteraser | Website and Server Security Solutions

🛡️ CVE-2026-5308 — mattermost-server

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-400 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Mattermost doesn't enforce request body size limits on plugin HTTP endpoints

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

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs administrative privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: High — administrative rights are needed first.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-5308 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

CVE-2026-5308 is recorded against 3 packages.

  • github.com/mattermost/mattermost-plugin-github
  • github.com/mattermost/mattermost-server
  • mattermost-server (from 11.6.0 up to 11.6.1)

Timeline and source

Published on 7 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Advisory)
nvd.nist.gov (Advisory)
github.com (Fix)
mattermost.com (Web)

Other advisories for this package

github.com/mattermost/mattermost-plugin-github has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-400: Uncontrolled Resource Consumption) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
CWE CWE-400
Public Exploit ✅ No
Source NVD
Published 2026-07-07
Updated 2026-08-20
Modified 2026-07-07

Affected Packages

Software From version Fixed in
github.com/mattermost/mattermost-plugin-github — —
github.com/mattermost/mattermost-server — —
mattermost-server 11.6.0 11.6.1

Similar Threats

Site Security Check

Is mattermost-server part of your stack?

CVE-2026-5308 is rated CVSS 8.0 High. BotEraser scans your installation against known CVE records and tells you whether this vulnerability applies to the versions you actually run.

Scan My Site Free →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

Browse related advisories

All advisoriesCVECVE 2026
✓