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Uncontrolled Resource Consumption

CVE-2026-49851

High
8.7/10

Summary

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.

  • LOW
  • NETWORK
  • NONE
  • NONE

CWE-400 - Uncontrolled resource consumption

An uncontrolled resource allocation attack (also known as resource exhaustion attack) triggers unauthorized overconsumption of the limited resources in an application, such as memory, file system storage, database connection pool entries, and CPU. This may lead to denial of service for valid users and degradation of the application's functionality as well as that of the host operating system.

References

Advisory Timeline

  • Published