CVE-2026-23986
HIGH
GHSA-4fqp-r85r-hxqh
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Lifecycle Timeline
4Description
Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, 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 to arbitrary directories outside the destination path by using directory a symlink along with `_preserve_symlinks: true` and a generated directory structure whose rendered path is inside the symlinked directory. 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. Version 9.11.2 patches the issue.
Analysis
Copier versions prior to 9.11.2 allow local attackers to write arbitrary files outside the intended project destination directory by exploiting symlink handling combined with the _preserve_symlinks feature in ostensibly safe templates. A malicious template author can craft a project template that bypasses security controls without requiring unsafe flags, enabling arbitrary file overwrites within the user's write permissions. …
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Remediation
Within 7 days: Identify all affected systems and apply vendor patches promptly. Vendor patch is available.
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External POC / Exploit Code
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