Denial of service via metadata regex backtracking
Published Oct 15, 2026 · Updated Oct 15, 2026
ReDoS in metadata parsing in Trent Mick markdown2 2.5.5 and earlier allows attackers to stall conversion via crafted Markdown. The _extract_metadata function in lib/markdown2.py applies _meta_data_pattern, whose overlapping repeated matches cause excessive regex processing of attacker-controlled metadata. The metadata extra must be enabled and untrusted documents must reach conversion; network exposure and required privileges depend on the consuming application.
Summary
What happened
ReDoS in metadata parsing in Trent Mick markdown2 2.5.5 and earlier allows attackers to stall conversion via crafted Markdown. The _extract_metadata function in lib/markdown2.py applies _meta_data_pattern, whose overlapping repeated matches cause excessive regex processing of attacker-controlled metadata. The metadata extra must be enabled and untrusted documents must reach conversion; network exposure and required privileges depend on the consuming application.
The record
- CVE
- CVE-2026-88753
- Published
- Oct 15, 2026
- Updated
- Oct 15, 2026
- Vendor
- Trent Mick
- Product
- markdown2
- Classifications
- T1499
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Oct 15, 2026CVE publishedPublication date reported by the CVE source.
- Oct 15, 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?
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- Affected versionversion=n/a
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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