Detections
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Mattermost Server 11.8.x < 11.8.6 Multiple Vulnerabilities

medium Web App Scanning Plugin ID 115686

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Synopsis

Mattermost Server 11.8.x < 11.8.6 Multiple Vulnerabilities

Description

According to its self-reported version number, the Mattermost Server application running on the remote host is 11.8.x prior to 11.8.6. It is, therefore, affected by multiple vulnerabilities:

- An issue where the bulk reactions endpoint accepted an unbounded post ID array, allowing an authenticated user to degrade availability (CVE-2026-95666).

- An issue where a request to a plugin route could be read without a size limit, allowing an authenticated user to exhaust server memory (CVE-2026-96260).

- An issue where the OAuth sign-in flow could issue requests to internal addresses configured by a System Administrator (CVE-2026-96259).

Note that the scanner has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Mattermost Server version 11.8.6 or later.

See Also

https://mattermost.com/security-updates

https://nvd.nist.gov/vuln/detail/CVE-2026-95666

https://nvd.nist.gov/vuln/detail/CVE-2026-96259

https://nvd.nist.gov/vuln/detail/CVE-2026-96260

Plugin Details

Severity: Medium

ID: 115686

Type: Version Based

Published: 10/16/2026

Updated: 10/16/2026

Scan Template: basic, full, pci, scan

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.61

CVSS v2

Risk Factor: Medium

Base Score: 6.8

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

CVSS Score Source: CVE-2026-96260

CVSS v3

Risk Factor: Medium

Base Score: 6.5

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

CVSS Score Source: CVE-2026-96260

Vulnerability Information

CPE: cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:*

Exploit Ease: No known exploits are available

Patch Publication Date: 9/22/2026

Vulnerability Publication Date: 9/21/2026

Reference Information

CVE: CVE-2026-95666, CVE-2026-96259, CVE-2026-96260