Pygments has Regular Expression Denial of Service (ReDoS) due to Inefficient Regex for GUID Matching
A security flaw has been discovered in pygments before 2.20.0. The impacted element is the function AdlLexer of the file pygments/lexers/archetype.py. The manipulation results in inefficient regular expression complexity. The attack is only possible with local access. The exploit has been released to the public and may be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pygments | < 2.20.0 | 2.20.0 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-4539
- https://github.com/pygments/pygments/issues/3058
- https://github.com/pygments/pygments/pull/3064
- https://github.com/pygments/pygments/commit/24b8aa76c6cd6d70f39c6dd605cce319c98e2ccc
- https://github.com/pygments/pygments
- https://github.com/pygments/pygments/releases/tag/2.20.0
- https://vuldb.com/?ctiid.352327
- https://vuldb.com/?id.352327
- https://vuldb.com/?submit.774685
- https://pypi.org/project/pygments
- https://github.com/advisories/GHSA-5239-wwwm-4pmq
- CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-1333, CWE-400- Platform
- Python (PyPI)
- Package
pygments- Disclosed
- 22.03.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2987 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5239-wwwm-4pmq - 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
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Pygments has Regular Expression Denial of Service (ReDoS) due to Inefficient Regex for GUID Matching this entry
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