🛡️ CVE-2026-4858 — mattermost-server

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-22 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Mattermost has a Path Traversal issue

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to check integration URL for path traversal which allows an malicious authenticated user to call an arbitrary API via system admin Mattermost auth token using via path traversal in integration action URL. Mattermost Advisory ID: MMSA-2026-00640.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs low-level privileges on the target. A user must be tricked into taking some action. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-4858 is classified as CWE-22: Path Traversal. A file path built from user input is not confined to the intended directory, letting an attacker reach files elsewhere on the filesystem.

Affected software

CVE-2026-4858 is recorded against 2 packages.

  • github.com/mattermost/mattermost-server
  • mattermost-server

Timeline and source

Published on 21 May 2026 and last revised on 25 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

nvd.nist.gov (Advisory)
github.com (Package)
mattermost.com (Web)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H
CWE CWE-22
Public Exploit ✅ No
Source NVD
Published 2026-05-21
Updated 2026-08-12
Modified 2026-06-25
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/mattermost/mattermost-server — —
mattermost-server — —

Similar Threats

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