CVE-2025-27516

A flaw was found in Jinja. In affected versions, an oversight in how the Jinja sandboxed environment interacts with the |attr filter allows an attacker who 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 that 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.

This vulnerability is rated as important severity due to the potential for an attacker to bypass Jinja's sandbox by exploiting the |attr filter, by controlling template content, an attacker can execute arbitrary Python code, impacting the integrity, confidentiality, and availability of the system. While the attack requires user interaction to trigger untrusted templates, the risk is significant in applications that allow such templates to be executed.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.