CVE-2026-4915
CWE-754Published: May 25, 2026· Updated: May 26, 2026
Official Description
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 filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
Technical Analysis
CVE-2026-4915 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Exploit & PoC Resources
All References (1)
Quick Facts
Related CVEs (CWE-754)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-4915 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts