Vulnerability · Published Jun 26, 2026 · Assigned by Mattermost

CVE-2026-13426Client4 fails to validate path parameters

Medium 5.4

In plain English

A medium-severity path traversal in github.com/mattermost/mattermost/server/public from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)0.3%top 78.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	github.com/mattermost/mattermost/server/public	0.1.22	GHSA-72v2-v53v-4qmm
Go	github.com/mattermost/mattermost/server/public	0.1.22	GO-2026-6910

Affected products (as reported)

Vendor	Product	Versions
Mattermost	github.com/mattermost/mattermost/server/public	v0.0.0 – before v0.1.22

Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

References

MMSA-2025-00532 vendor-advisory