CVE•Published 2026-05-18•Modified 2026-05-19•0 articles on news•5 live references•NVD data

CVE-2026-6340Mattermost · Mattermost_server

Vulnerability data via NVD (ingested)

CVSS v3.1

4.3

MEDIUM

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

EPSS percentile

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Weaknesses (CWE)

CWE-789Memory Allocation with Excessive Size Value

Description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.. Mattermost Advisory ID: MMSA-2026-00573

Timeline

Published 2026-05-18

Modified 2026-05-19

External references

NVD MITRE Exploit-DB 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-2026-6340

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-2026-6340