CVE-2026-6339: mattermost server from 11.4.0 (inclusive), before 11.4.4 (exclusive), from 11.5.0 (inclusive), before 11.5.2…

Affected technology

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, 11.4.0 through 11.4.3
Mattermost

Description’s affected range: versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint 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

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 4.3/10) rates confidentiality impact as low; integrity and availability impact as none. The description does not specify what an attacker can achieve beyond these rated impacts.