CVE-2026-13426

Client4 fails to validate path parameters

5.4 MediumFix available

The Mattermost Go module github.com/mattermost/mattermost/server/public versions < v0.1.22 fail to validate path parameters when constructing API route paths which allows an attacker to redirect API calls to unintended endpoints via crafted IDs containing path traversal components. Mattermost Advisory ID: MMSA-2025-00532

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.29%Up 0.1 points since Jun 27, 2026

What each source reports

CVE List Score used 5.4

Client4 fails to validate path parameters

Record: CVE-2026-13426
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-22
Updated: 2026-11-02

EUVDEUVD-2026-39661 5.4

Record: EUVD-2026-39661
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-72v2-v53v-4qmm 5.4

github.com/mattermost/mattermost/server/public vulnerable to path traversal in API route construction

Record: GHSA-72v2-v53v-4qmm
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-22
Updated: 2026-11-03

NVD 5.4

Record: CVE-2026-13426
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-22
Updated: 2026-11-02

OSVGHSA-72v2-v53v-4qmm 5.4

github.com/mattermost/mattermost/server/public vulnerable to path traversal in API route construction

Record: GHSA-72v2-v53v-4qmm
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-22
Updated: 2026-11-06

OSVGO-2026-6910 No score

Path traversal in API route construction in github.com/mattermost/mattermost/server/public

Path traversal in API route construction in github.com/mattermost/mattermost/server/public

Record: GO-2026-6910
Updated: 2026-11-06

Affected products

mattermost github.com/mattermost/mattermost/server/public

Affected packages

Affected packages
Package	Affected	Fixed
`github.com/mattermost/mattermost/server/public` Go	before 0.1.22	0.1.22

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, aliases, references	OSV
Nov 3, 2026	affected, facts, references	GitHub Advisories, OSV
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-13426 is a medium vulnerability (CVSS 5.4) in Mattermost Github.com/mattermost/mattermost/server/public, published June 26, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.29%, the 21st percentile. Fixed in github.com/mattermost/mattermost/server/public 0.1.22.