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Moderate severityNVD Advisory· Published Mar 5, 2025· Updated Feb 26, 2026

Jinja sandbox breakout through attr filter selecting format method

CVE-2025-27516

Description

Jinja is an extensible templating engine. Prior to 3.1.6, 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. This vulnerability is fixed in 3.1.6.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
Jinja2PyPI
< 3.1.63.1.6

Affected products

66

Patches

Vulnerability mechanics

References

6

News mentions

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