What is CVE-2026-59922?

CVE-2026-59922 is a high-severity vulnerability in Lepture Mistune, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-07-08.

How severe is CVE-2026-59922?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Lepture Mistune

CVE-2026-59922

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

Published 2026-07-08 · last modified 2026-07-09.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.006 (49.3th percentile), scored 2026-10-09.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Lepture Mistune — versions < 3.3.0
Mistune Project

Weakness classification (CWE)

References

github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq (Exploit, Vendor Advisory)
github.com/lepture/mistune/commit/96d0f57f8fe9eeb06bb4cff521962a27d7c402e7 (Patch)
github.com/lepture/mistune/releases/tag/v3.3.0 (Release Notes)

Frequently asked questions

What is CVE-2026-59922?: CVE-2026-59922 is a high-severity vulnerability in Lepture Mistune, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-07-08.
How severe is CVE-2026-59922?: High severity. CVSS v3 base score is 7.5 out of 10.