Mattermost Markdown autolink parsing denial of service
Summary
| CVE | CVE-2026-12882 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-14 11:17:03 UTC |
| Updated | 2026-09-16 19:30:49 UTC |
| Description | Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to parse Markdown autolinks with unmatched trailing closing parentheses in linear time, which allows an authenticated user with permission to create posts to cause excessive server CPU consumption and degrade availability for other users via specially crafted post or message attachment content. Mattermost Advisory ID: MMSA-2026-00703 |
Risk And Classification
Primary CVSS: v3.1 4.3 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
EPSS: 0.002120000 probability, percentile 0.116830000 (date 2026-09-16)
Problem Types: CWE-407 | CWE-407 CWE-407: Inefficient Algorithmic Complexity
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 4.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
| 3.1 | CNA | CVSS | 4.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
LowCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.9.0 11.9.0 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.8.0 11.8.4 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.7.0 11.7.7 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 10.11.0 10.11.22 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.10.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.9.1 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.8.5 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.8 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.23 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Adam Korczynski (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.
There are currently no legacy QID mappings associated with this CVE.