markdown2 >=1.0.1.18, fixed in 2.4.0, is affected by a regular expression denial of…
Priority LOW 37CWE-1333Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-1333.
Summary
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.
Why it matters now
EPSS 0.02319 83rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed markdown2 (PyPI): 2.4.0
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
| — | markdown2 (PyPI) | 1.0.1.18 to before 2.4.0 | 2.4.0 | Patch available | GHSA-jr9p-r423-9m2r |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
- markdown2 (PyPI) Vendor— Affected 1.0.1.18 to before 2.4.0 Fixed in 2.4.0 Patch available GHSA-jr9p-r423-9m2r
CPE configurations NVD · 4
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:markdown2_project:markdown2:*:*:*:*:*:*:*:* | 1.0.1.18 to before 2.4.0 | Vulnerable | Markdown2 Project |
| cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* | 32 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* | 33 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* | 34 | Vulnerable | Fedoraproject |
- cpe:2.3:a:markdown2_project:markdown2:*:*:*:*:*:*:*:* Versions 1.0.1.18 to before 2.4.0 Vulnerable ·Markdown2 Project
- cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* Versions 32 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject
Remediation
- Fix · GHSA-jr9p-r423-9m2r markdown2 (PyPI) Fixed in 2.4.0 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2021-26813
- 2026-10-03 Alias added: GHSA-jr9p-r423-9m2r
References
Advisory 5
Other 6
- 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/[email protected]/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5
- https://lists.fedoraproject.org/archives/list/[email protected]/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH
- https://lists.fedoraproject.org/archives/list/[email protected]/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY
Sources
- CVE-2021-26813 · CVE Program
- CVE-2021-26813 · NVD
- FIRST EPSS
- GHSA-jr9p-r423-9m2r · GitHub Advisory Database · CC BY 4.0
- CVE-2021-26813 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences