DoS Vulnerability in Mistune Python Markdown Parser
CVE-2026-59922

7.5HIGH

Key Information:

Vendor

Lepture

Status
Mistune
Vendor
CVE Published:
8 July 2026

What is CVE-2026-59922?

The Mistune Python Markdown parser, prior to version 3.3.0, is susceptible to a denial of service attack. When processing runs with specific pairs of markers (closed tilde, equals-sign, or caret), the parser can perform quadratic work due to inefficient scanning for matching markers. This can lead to significant CPU exhaustion, potentially crippling the performance of applications using this library. Users are urged to upgrade to version 3.3.0 or later to mitigate this issue.

Affected Version(s)

mistune < 3.3.0

References

https://github.com/lepture/mistune/security/advisories/GH...
x_refsource_CONFIRM
https://github.com/lepture/mistune/commit/96d0f57f8fe9eeb...
x_refsource_MISC
https://github.com/lepture/mistune/releases/tag/v3.3.0
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.