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Mattermost is vulnerable to CPU exhaustion via crafted HTTP request

Low severity GitHub Reviewed Published Jan 16, 2026 to the GitHub Advisory Database • Updated Jan 16, 2026

Package

gomod github.com/mattermost/mattermost-server (Go)

Affected versions

>= 10.11.0, <= 10.11.8
>= 11.0.0, < 11.2.0

Patched versions

10.11.9
11.2.0
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20251201064648-4d86263f5430
8.0.0-20251201064648-4d86263f5430

Description

Mattermost versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens.

References

Published by the National Vulnerability Database Jan 16, 2026
Published to the GitHub Advisory Database Jan 16, 2026
Last updated Jan 16, 2026
Reviewed Jan 16, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(11th percentile)

Weaknesses

Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached. Learn more on MITRE.

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. Learn more on MITRE.

CVE ID

CVE-2025-14822

GHSA ID

GHSA-9r42-rhw3-2222

Source code

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