Vulnerability · Published Jan 21, 2026 · Assigned by GitHub_M
CVE-2026-23986Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true
Medium 6.9
In plain English
A medium-severity security flaw in copier from copier-org. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | copier | 9.11.2 | GHSA-4fqp-r85r-hxqh |
| PyPI | copier | 9.11.2 | PYSEC-2026-1272 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| copier-org | copier | < 9.11.2 |
Weakness: CWE-61 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N