Critical Security Flaw in python-jinja2: Jinja Sandbox Breakout Vulnerability
Summary
RLSA-2025:3406: Important: python-jinja2 security update. Affects python-jinja2 versions < 0:2.11.3-8.el9_5. Fixed in 0:2.11.3-8.el9_5. How to fix ↓
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Background
python-jinja2 is a popular templating engine for Python, widely used for rendering dynamic web pages. It allows developers to create templates that can be populated with data, enabling the separation of presentation and logic. The package supports features like template inheritance, macros, and filters, making it a powerful tool for web development. However, it has recently been identified as vulnerable to a security issue that could allow unauthorized access to sensitive data.
Vulnerability Detail
The vulnerability, identified as CVE-2025-27516, arises from a flaw in the Jinja sandbox that allows a malicious actor to exploit the 'attr' filter to select the 'format' method. This could lead to a sandbox breakout, enabling attackers to execute arbitrary code and potentially gain access to sensitive information. The CVSS score for this vulnerability is 7.3, indicating a high severity level, which necessitates immediate attention from developers using this package.
How To Fix
Minimum fixed version
0:2.11.3-8.el9_5
This is the first release that contains the fix.
sudo dnf update python-jinja2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, if updating the package is not immediately feasible, consider restricting the use of the 'attr' filter in your templates until the patch is applied. This can help mitigate the risk of exploitation while you prepare for a full update.
Conclusion
The python-jinja2 package has a critical vulnerability that could lead to serious security breaches if not addressed. It is crucial for developers to update to the patched version promptly and consider temporary workarounds to mitigate risks. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
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FAQ
CVE-2025-27516 is a security vulnerability in the python-jinja2 package that allows for a sandbox breakout through the 'attr' filter.
The vulnerability has a CVSS score of 7.3, indicating a high severity level that requires prompt action.
Exploitation of this vulnerability could allow attackers to execute arbitrary code and access sensitive data within the application.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
If immediate updates are not possible, restrict the use of the 'attr' filter in your templates as a temporary workaround.
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