Regular Expression Denial of Service (ReDoS) in Jinja2
This affects the package jinja2 from 0.0.0 and before 2.11.3. The ReDOS vulnerability of the regex is mainly due to the sub-pattern [a-zA-Z0-9.-]+.[a-zA-Z0-9.-]+ This issue can be mitigated by Markdown to format user content instead of the urlize filter, or by implementing request timeouts and limiting process memory.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jinja2 | < 2.11.3 | 2.11.3 |
References
- https://github.com/pallets/jinja/blob/ab81fd9c277900c85da0c322a2ff9d68a235b2e6/src/jinja2/utils.py%23L20
- https://github.com/pallets/jinja/pull/1343
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-1012994
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVAKCOO7VBVUBM3Q6CBBTPBFNP5NDXF4/
- https://github.com/advisories/GHSA-g3rq-g295-4j3m
- https://nvd.nist.gov/vuln/detail/CVE-2020-28493
- https://github.com/pallets/jinja/commit/15ef8f09b659f9100610583938005a7a10472d4d
- https://github.com/pallets/jinja
- https://github.com/pypa/advisory-database/tree/main/vulns/jinja2/PYSEC-2021-66.yaml
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVAKCOO7VBVUBM3Q6CBBTPBFNP5NDXF4
- https://security.gentoo.org/glsa/202107-19
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
jinja2- Disclosed
- 01.02.2021
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-66 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-g3rq-g295-4j3m - CC BY 4.0
Vulnerability history: jinja2
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
- 11
- First → latest
- 05.2014 06.2025
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 7
Disclosures per year
- 2017: 0
- 2018: 0
- 2019: 2
- 2020: 0
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 4
- 2025: 2
- 2026: 0
earlier: 2
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Regular Expression Denial of Service (ReDoS) in Jinja2 this entry
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