CVE•Published 2026-05-25•Modified 2026-06-01•0 articles on news•6 live references•NVD data

CVE-2026-4915Mattermost · Mattermost_server

Vulnerability data via NVD (ingested)

CVSS v3.1

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS percentile

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Weaknesses (CWE)

CWE-754Improper Check for Unusual or Exceptional Conditions

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

Timeline

Published 2026-05-25

Modified 2026-06-01

External references

NVD MITRE Exploit-DB GitHub PoC Sploitus VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-4915

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Mattermost Mattermost Server"

All exposed Mattermost Mattermost Server instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Mattermost Server"

HTTP body or banner mentions "Mattermost Server" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-4915