CVE-2025-55201: Copier safe template has arbitrary filesystem read/write access

Severity: high (CVSS 8.5 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-08-18 · updated 2026-06-17
Weakness: CWE-22

Description

Copier library and CLI app for rendering project templates. Prior to 9.9.1, a safe template can currently read and write arbitrary files because Copier exposes a few pathlib.Path objects in the Jinja context which have unconstrained I/O methods. This effectively renders the security model w.r.t. filesystem access useless. This vulnerability is fixed in 9.9.1.

Affected products

copier-org copier: before 9.9.1

References

https://github.com/copier-org/copier/commit/3feea3b3ff3c20d80cbb16a2f3b9567ffc5606d1
https://github.com/copier-org/copier/security/advisories/GHSA-3xw7-v6cj-5q8h

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