markdown2 Regular Expression Denial of Service
markdown2 >=1.0.1.18, fixed in 2.4.0, is affected by a regular expression denial of service vulnerability. If an attacker provides a malicious string, it can make markdown2 processing difficult or delayed for an extended period of time.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | markdown2 | >= 1.0.1.18, < 2.4.0 | 2.4.0 |
References
- https://github.com/trentm/python-markdown2/pull/387
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH/
- https://github.com/advisories/GHSA-jr9p-r423-9m2r
- https://nvd.nist.gov/vuln/detail/CVE-2021-26813
- https://github.com/trentm/python-markdown2/commit/7b651260739647de5198323e0445b1618750c374
- https://github.com/pypa/advisory-database/tree/main/vulns/markdown2/PYSEC-2021-20.yaml
- https://github.com/trentm/python-markdown2
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-1333- Platform
- Python (PyPI)
- Package
markdown2- Disclosed
- 03.03.2021
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-20 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-jr9p-r423-9m2r - CC BY 4.0
Vulnerability history: markdown2
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 01.2018 03.2021
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 3
Disclosures per year
- 2018: 1
- 2019: 0
- 2020: 2
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
-
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