Pygments vulnerable to Regular Expression Denial of Service (ReDoS)
In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. By crafting malicious input, an attacker can cause a denial of service.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pygments | >= 1.1, < 2.7.4 | 2.7.4 |
References
- https://gist.github.com/b-c-ds/b1a2cc0c68a35c57188575eb496de5ce
- https://github.com/pygments/pygments/commit/2e7e8c4a7b318f4032493773732754e418279a14
- https://lists.debian.org/debian-lts-announce/2021/03/msg00024.html
- https://www.debian.org/security/2021/dsa-4878
- https://www.debian.org/security/2021/dsa-4889
- https://lists.debian.org/debian-lts-announce/2021/05/msg00003.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WSLD67LFGXOX2K5YNESSWAS4AGZIJTUQ/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GSJRFHALQ7E3UV4FFMFU2YQ6LUDHAI55/
- https://lists.debian.org/debian-lts-announce/2021/05/msg00006.html
- https://github.com/advisories/GHSA-pq64-v7f5-gqh8
- https://nvd.nist.gov/vuln/detail/CVE-2021-27291
- https://github.com/pygments/pygments
- https://github.com/pypa/advisory-database/tree/main/vulns/pygments/PYSEC-2021-141.yaml
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GSJRFHALQ7E3UV4FFMFU2YQ6LUDHAI55
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WSLD67LFGXOX2K5YNESSWAS4AGZIJTUQ
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
pygments- Disclosed
- 17.03.2021
- Updated
- 11.10.2026 11:20
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-141 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-pq64-v7f5-gqh8 - CC BY 4.0
Vulnerability history: pygments
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
- 5
- First → latest
- 01.2016 03.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 2
- Medium 1
- Low 1
Disclosures per year
- 2017: 0
- 2018: 0
- 2019: 0
- 2020: 0
- 2021: 2
- 2022: 0
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 1
earlier: 1
-
Pygments vulnerable to Regular Expression Denial of Service (ReDoS) this entry
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