Authenticated denial of service via nonlinear autolink parsing
Published Sep 14, 2026 · Updated Sep 14, 2026
Inefficient Markdown parsing in affected Mattermost Server releases allows remote authenticated users to degrade availability through crafted posts. The server's Markdown autolink parser processes unmatched trailing closing parentheses with nonlinear work, driving excessive CPU consumption. An account permitted to create posts is required; crafted post text or message-attachment content can slow service for other users.
Summary
What happened
Inefficient Markdown parsing in affected Mattermost Server releases allows remote authenticated users to degrade availability through crafted posts. The server's Markdown autolink parser processes unmatched trailing closing parentheses with nonlinear work, driving excessive CPU consumption. An account permitted to create posts is required; crafted post text or message-attachment content can slow service for other users.
The record
- CVE
- CVE-2026-12882
- Published
- Sep 14, 2026
- Updated
- Sep 14, 2026
- Vendor
- Mattermost
- Product
- Mattermost
- Classifications
- T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 14, 2026CVE publishedPublication date reported by the CVE source.
- Sep 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.11.0 <=10.11.22
- Affected versionversion=11.7.0 <=11.7.7
- Affected versionversion=11.8.0 <=11.8.4
- Affected versionversion=11.9.0 <=11.9.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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