CVE-2025-55214
- Published: 2025-08-18T17:15:30.310
Copier library and CLI app for rendering project templates. From 7.1.0 to before 9.9.1, Copier suggests that it’s safe to generate a project from a safe template, i.e. one that doesn’t use unsafe features like custom Jinja extensions which would require passing the –UNSAFE,–trust flag. As it turns out, a safe template can currently write files outside the destination path where a project shall be generated or updated. This is possible when rendering a generated directory structure whose rendered path is either a relative parent path or an absolute path. Constructing such paths is possible using Copier’s builtin pathjoin Jinja filter and its builtin _copier_conf.sep variable, which is the platform-native path separator. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user’s write permissions), e.g., to cause havoc. This vulnerability is fixed in 9.9.1.
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How to fix CVE-2025-55214
Description: Copier library and CLI app for rendering project templates. From 7.1.0 to before 9.9.1, Copier suggests that it’s safe to generate a project from a safe template, i.e. one that doesn’t use unsafe features like custom Jinja extensions which would require passing the –UNSAFE,–trust flag. As it turns out, a safe template can currently write […]
Exploit Difficulty: HARD
⏱️ Time to exploit: > 4 hours
🛠️ Required skills: Advanced security expertise
💰 Public exploits: Rare or not public
How to Fix:
- Check if you're running the affected product
- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access
- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)
- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations
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