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Mattermost allows attackers to spoof permalink embeds

Moderate severity GitHub Reviewed Published Mar 16, 2026 to the GitHub Advisory Database • Updated Mar 17, 2026

Package

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

Affected versions

< 5.3.2-0.20260123211116-9efe617be8b8
>= 10.11.0-rc1, < 10.11.11
>= 11.2.0-rc1, < 11.2.3
>= 11.3.0-rc1, < 11.3.1

Patched versions

5.3.2-0.20260123211116-9efe617be8b8
10.11.11
11.2.3
11.3.1
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20260123211116-9efe617be8b8
8.0.0-20260123211116-9efe617be8b8

Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to sanitize client-supplied post metadata which allows an authenticated attacker to spoof permalink embeds impersonating other users via crafted PUT requests to the post update API endpoint. Mattermost Advisory ID: MMSA-2025-00569

References

Published by the National Vulnerability Database Mar 16, 2026
Published to the GitHub Advisory Database Mar 16, 2026
Reviewed Mar 17, 2026
Last updated Mar 17, 2026

Severity

Moderate

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
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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:L/PR:L/UI:N/S:U/C:N/I:L/A:N

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.
(3rd percentile)

Weaknesses

Origin Validation Error

The product does not properly verify that the source of data or communication is valid. Learn more on MITRE.

CVE ID

CVE-2026-2457

GHSA ID

GHSA-ph22-fw5m-w2q9

Source code

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