CVE-2026-6850

🔶 medium

Summary

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658

CVSS Score

6.5

Medium

EPSS Score

0.2

Exploit Probability

Published Date

2026-07-13

First Seen: 2026-07-14

📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 47.6% of all 338,292 vulnerabilities in our database.

#177,181

Below average severity

Severity Percentile

🎯 CISA SSVC Assessment Updated: Jul 13, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

Requires human interaction

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

idr

SSVC data provided by CISA

Last Modified 2026-07-13

Source NVD 🔗

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

CWE IDs (Weakness Types)

CWE-1333

📦 Affected Products 3

Vendor	Product	Status	Affected Versions
mattermost	mattermost_server	Affected	> 10.11.0 < 10.11.20
mattermost	mattermost_server	Affected	> 11.6.0 < 11.6.5
mattermost	mattermost_server	Affected	> 11.7.0 < 11.7.3

🔗 References 1

https://mattermost.com/security-updates

Vendor Advisory

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-10085	🔶 medium	5.4	0.2	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to restrict the group_constrained chann...	2026-07-13
CVE-2026-10103	🔶 medium	4.3	0.2	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify post ownership in the shared ...	2026-07-13
CVE-2026-10106	🔶 medium	6.5	0.2	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify that the channel referenced i...	2026-07-13
CVE-2026-9571	🔶 medium	5.9	0.2	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon...	2026-07-13
CVE-2026-9597	🔶 medium	5.4	0.1	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before crea...	2026-07-13
CVE-2026-9708	🔶 medium	4.9	0.2	Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming w...	2026-07-13

These CVEs affect the same products