CVE-2026-6850
Crafted message attachment causes client-side denial of service via markdown parser regex backtracking in Mattermost
CVSS Score
6.5
EPSS Score
0.2%
EPSS Percentile
14th
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
| CWE | CWE-1333 |
| Vendor | mattermost |
| Product | mattermost |
| Published | Jul 13, 2026 |
| Last Updated | Jul 13, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
Mattermost / Mattermost
11.7.0 ≤ 11.7.2 11.6.0 ≤ 11.6.4 10.11.0 ≤ 10.11.19
Credits
idr