CVE-2026-6340: mattermost server from 10.11.0 (inclusive), before 10.11.14 (exclusive), from 11.4.0 (inclusive), before 11.4.4…

Affected technology

mattermost server · from 10.11.0 (inclusive), before 10.11.14 (exclusive)
mattermost

mattermost server · from 11.4.0 (inclusive), before 11.4.4 (exclusive)
mattermost

mattermost server · from 11.5.0 (inclusive), before 11.5.2 (exclusive)
mattermost

Mattermost · 11.5.0 through 11.5.1, 10.11.0 through 10.11.13, 11.4.0 through 11.4.3
Mattermost

Description’s affected range: 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

Component: Not specified by the source

Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · Low privileges required · No user interaction required

Attack conditions (NVD, CVSS 3.1): Network (remote) · Low privileges required · No user interaction required

What an attacker can do

An authenticated attacker can cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations. Vendor/CNA’s CVSS 3.1 assessment (base score 4.3/10) rates confidentiality and integrity impact as none; availability impact as low. NVD’s CVSS 3.1 assessment (base score 6.5/10) rates confidentiality and integrity impact as none; availability impact as high.