Cyber Resilience

CVE-2026-4858

High

Published: 21 May 2026

Published
21 May 2026
Modified
21 May 2026
KEV Added
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Patch
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CVSS Score v3.1 8.0 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H
EPSS Score 0.0025 16.2th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-4858 is a high-severity Path Traversal (CWE-22) vulnerability in Mattermost Mattermost Server. Its CVSS base score is 8.0 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 16.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability details

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…

more

via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640

CWE(s)
CWE-22

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

Path traversal in integration URL enables authenticated user to invoke arbitrary (including privileged) APIs, directly facilitating exploitation of the public-facing app and privilege escalation.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2025-25279Same product: Mattermost Mattermost Server
CVE-2025-20051Same product: Mattermost Mattermost Server
CVE-2025-14273Same product: Mattermost Mattermost Server
CVE-2025-24490Same product: Mattermost Mattermost Server
CVE-2025-20621Same product: Mattermost Mattermost Server
CVE-2025-25274Same product: Mattermost Mattermost Server
CVE-2025-12421Same product: Mattermost Mattermost Server
CVE-2025-25068Same product: Mattermost Mattermost Server
CVE-2025-12419Same product: Mattermost Mattermost Server
CVE-2026-20719Same product: Mattermost Mattermost Server

Affected Assets

mattermost
mattermost server
11.6.0 · 10.11.0 — 10.11.15 · 11.4.0 — 11.4.5 · 11.5.0 — 11.5.4

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-10 Information Input Validation
addresses: CWE-22

Validates pathnames and filenames to prevent traversal outside intended directories.

References