CVE-2026-5163

May 18, 2026, 7:12 p.m.

6.5
Medium

Description

Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645

Product(s) Impacted

Vendor Product Versions
Mattermost
  • Mattermost Server
  • *

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-862
Missing Authorization
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

*CPE(s)

Affected systems and software identified for this CVE.

Type Vendor Product Version Update Edition Language Software Edition Target Software Target Hardware Other Information
a mattermost mattermost_server / / / / / / / /

References

https://mattermost.com/security-updates

Tags

CWE-862
[email protected]
2026-05-18
CVE-2026-5163

CVSS Score

6.5 / 10

CVSS Data - 3.1

  • Attack Vector: NETWORK
  • Attack Complexity: LOW
  • Privileges Required: LOW
  • Scope: UNCHANGED
  • Confidentiality Impact: HIGH
  • Integrity Impact: NONE
  • Availability Impact: NONE

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

    View Vector String

Timeline

Published: May 18, 2026, 9:16 a.m.
Last Modified: May 18, 2026, 7:12 p.m.

Status : Analyzed

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

[email protected]

*Disclaimer: Some vulnerabilities do not have an associated CPE. To enhance the data, we use AI to infer CPEs based on CVE details. This is an automated process and might not always be accurate.