EUVD-2026-65137Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Network-delivered crafted input requires no auth or interaction; impact is strictly process availability loss with no confidentiality or integrity effect.
Primary rating from Vendor (github).
CVSS VectorVendor: github
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4DescriptionCVE.org
Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to DoS through deeply nested tokens. HTML rendering creates deeply nested emphasis tokens from consecutive asterisk characters, and recursive rendering in HTMLRenderer.render_token() can exceed Python's recursion limit and raise RecursionError, allowing crafted Markdown to crash a parsing process. This issue is fixed in version 3.3.3
Articles & Coverage 1
AnalysisAI
Denial-of-service in Mistune Python Markdown parser versions 3.3.0-3.3.2 allows remote unauthenticated attackers to crash any process that renders user-supplied Markdown by submitting input with hundreds of consecutive asterisk characters. The recursive HTMLRenderer.render_token() traversal grows proportionally to emphasis nesting depth and exceeds Python's default recursion limit, raising an unhandled RecursionError that terminates the parsing process. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The target application must accept user-supplied content and pass it to Mistune 3.3.0-3.3.2 for parsing and HTML rendering - this is the sole prerequisite. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 7.5 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) is well-supported by the technical evidence: any network-reachable endpoint that pipes user input into Mistune 3.3.0-3.3.2 is exploitable with a single, trivially crafted HTTP request. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker submits a POST request to a web application's comment or document-rendering endpoint with a Markdown body consisting of 1000 asterisks, a single letter, and 1000 more asterisks. Mistune 3.3.x builds an unbounded nested emphasis token tree from this input, and the recursive HTMLRenderer.render_token() call exhausts Python's default recursion limit, raising RecursionError and crashing the worker process or thread. … |
| Remediation | The primary remediation is upgrading Mistune to version 3.3.3, which caps emphasis token nesting at a configurable depth (default 20) before recursive rendering can exhaust the Python call stack. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, scan all systems and applications to identify instances of Mistune versions 3.3.0-3.3.2 through dependency management and inventory tools. …
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Same weakness CWE-674 – Uncontrolled Recursion
View allSame technique Denial Of Service
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External POC / Exploit Code
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