CVE-2026-23986
BaseFortify
Publication date: 2026-01-21
Last updated on: 2026-02-02
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| copier-org | copier | to 9.11.2 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-61 | The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Copier library and CLI app for rendering project templates. Before version 9.11.2, Copier incorrectly considers certain templates safe if they do not use unsafe features like custom Jinja extensions. However, a so-called safe template can exploit a combination of directory symlinks with the _preserve_symlinks: true setting and a crafted directory structure to write files outside the intended destination path. This allows a malicious template author to overwrite arbitrary files on the user's system, limited only by the user's write permissions. Version 9.11.2 fixes this issue.
How can this vulnerability impact me? :
This vulnerability can allow a malicious template to overwrite arbitrary files on your system outside the intended project directory. This could lead to data loss, corruption, or unauthorized modification of files, potentially causing system instability or security breaches depending on which files are overwritten. The impact depends on the user's write permissions, so if the user has high privileges, the damage could be significant.
What immediate steps should I take to mitigate this vulnerability?
Upgrade Copier to version 9.11.2 or later, as this version patches the vulnerability. Avoid generating projects from templates that use unsafe features or require the --UNSAFE or --trust flags unless you fully trust the template source. Additionally, be cautious of templates that use symlinks with _preserve_symlinks: true to prevent arbitrary file overwrites.