Process crash via recursively rendered emphasis tokens
Published Aug 24, 2026 · Updated Aug 24, 2026
Uncontrolled recursion in Mistune 3.3.0 through 3.3.2 allows remote attackers to crash Markdown-parsing processes via crafted input. InlineParser creates deeply nested emphasis tokens from consecutive asterisks, and HTMLRenderer.render_token() recursively renders their children until Python raises RecursionError. Exposure requires an application to pass attacker-controlled Markdown to Mistune's HTML renderer; the resulting exception interrupts the affected parsing process.
Summary
What happened
Uncontrolled recursion in Mistune 3.3.0 through 3.3.2 allows remote attackers to crash Markdown-parsing processes via crafted input. InlineParser creates deeply nested emphasis tokens from consecutive asterisks, and HTMLRenderer.render_token() recursively renders their children until Python raises RecursionError. Exposure requires an application to pass attacker-controlled Markdown to Mistune's HTML renderer; the resulting exception interrupts the affected parsing process.
The record
- CVE
- CVE-2026-76098
- Published
- Aug 24, 2026
- Updated
- Aug 24, 2026
- Vendor
- Lepture
- Product
- Mistune
- Classifications
- CWE-674, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 24, 2026CVE publishedPublication date reported by the CVE source.
- Aug 24, 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=>= 3.3.0, < 3.3.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
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
- Mistune excessive-emphasis RecursionError proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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