Allocation of Resources Without Limits or Throttling Affecting mistune package, versions [,3.3.0)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PYTHON-MISTUNE-17458804
- published25 Jun 2026
- disclosed24 Jun 2026
- creditbhanugoudm041
Introduced: 24 Jun 2026
CVE-2026-49851 (opens in a new tab)How to fix?
Upgrade mistune to version 3.3.0 or higher.
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in the parse_link_text function of mistune/inline_parser.py, which performs a regex search inside a loop that advances one character at a time when parsing fails, producing O(n²) behavior. An attacker can exhaust CPU and cause denial of service by submitting a small Markdown payload of consecutive [ characters, around 6 KB, to any path that parses it, with no authentication required. Exploitation depends only on the application parsing untrusted Markdown.