Vulnerability in Lepture Mistune
CVE-2026-59928
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
EPSS: 0.004 (34.7th percentile) — read the EPSS interpretation.
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.
Affected products
- Lepture Mistune — versions < 3.3.0
- Mistune_project Mistune
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Third Party Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-59928?
- CVE-2026-59928 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-2026-59928?
- High severity. CVSS v3 base score is 7.5 out of 10.