Authentication Bypass in Mattermost Client-side Metadata Handling
CVE-2026-2457

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 March 2026

What is CVE-2026-2457?

The Mattermost platform contains a vulnerability where versions 11.3.x up to 11.3.0, 11.2.x up to 11.2.2, and 10.11.x up to 10.11.10 do not properly sanitize client-supplied post metadata. This weakness allows an authenticated attacker to perform spoofing of permalink embeds by sending crafted PUT requests to the post update API endpoint. Such an attack could potentially mislead users by impersonating other users, making it a critical concern for the integrity and trust within user interactions on the platform. For further details, please refer to the Mattermost Advisory (MMSA-2025-00569).

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Affected Version(s)

Mattermost 11.3.0

Mattermost 11.2.0 <= 11.2.2

Mattermost 10.11.0 <= 10.11.10

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

daw10
JSON
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