Jinja2 vulnerable to sandbox breakout through attr filter selecting format method
An oversight in how the Jinja sandboxed environment interacts with the |attr filter allows an attacker that controls the content of a template to execute arbitrary Python code.
To exploit the vulnerability, an attacker needs to control the content of a template. Whether that is the case depends on the type of application using Jinja. This vulnerability impacts users of applications which execute untrusted templates.
Jinja's sandbox does catch calls to str.format and ensures they don't escape the sandbox. However, it's possible to use the |attr filter to get a reference to a string's plain format method, bypassing the sandbox. After the fix, the |attr filter no longer bypasses the environment's attribute lookup.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jinja2 | < 3.1.6 | 3.1.6 |
References
- https://github.com/pallets/jinja/security/advisories/GHSA-cpwx-vrp4-4pq7
- https://nvd.nist.gov/vuln/detail/CVE-2025-27516
- https://github.com/pallets/jinja/commit/90457bbf33b8662926ae65cdde4c4c32e756e403
- https://github.com/pallets/jinja
- https://lists.debian.org/debian-lts-announce/2025/04/msg00022.html
- https://lists.debian.org/debian-lts-announce/2025/04/msg00045.html
- https://pypi.org/project/jinja2
- https://github.com/advisories/GHSA-cpwx-vrp4-4pq7
- CVSS vector
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-1336- Platform
- Python (PyPI)
- Package
jinja2- Disclosed
- 05.03.2025
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1471 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-cpwx-vrp4-4pq7 - 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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Jinja2 vulnerable to sandbox breakout through attr filter selecting format method this entry
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