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SCA: security update for github.com/mattermost/mattermost-server, github.com/mattermost/mattermost/server/v8 (GHSA-8r89-8w26-cq32)

medium Tenable Self-Hosted Container Security Plugin ID 442572

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - 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 (CVE-2026-5163)

Solution

Update the github.com/mattermost/mattermost/server/v8 library and its related packages to version 11.5.2 or later.

See Also

https://github.com/advisories/GHSA-8r89-8w26-cq32

Plugin Details

Severity: Medium

ID: 442572

Version: Revision 1.3

Type: Local

Family: SCA Checks

Published: 6/2/2026

Updated: 7/2/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.71

Vendor

Vendor Severity: Medium

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:N/A:N

CVSS Score Source: CVE-2026-5163

CVSS v3

Risk Factor: Medium

Base Score: 6.5

Temporal Score: 5.7

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Patch Publication Date: 5/18/2026

Vulnerability Publication Date: 5/18/2026

Reference Information

CVE: CVE-2026-5163

cwe: CWE-862