CVE-2026-53951

Copier is a library and CLI app for rendering project templates. In versions 9.5.0 through 9.15.1, the `trust` setting's prefix match (`copier/_settings.py`) compares the template URL against a trusted prefix with a raw `str.startswith` and no path normalization, while the URL is normalized when the template is actually fetched (`Path.resolve()` for local paths; libcurl dot-segment removal for `https`). A template reference that textually starts with a trusted prefix but contains `..` is therefore granted trust yet resolves to a different, attacker-controlled template, whose `tasks` / `migrations` / `jinja_extensions` then run without the `--trust` prompt — arbitrary command execution. Version 9.15.2 patches the issue.

CVSS 4.0

8.8CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 17% of CVEs (scores of 2026-10-25)

CWEs

CWE-22, CWE-94

Published

2026-07-08

Modified

2026-10-25

Record from

the NVD, synced 2026-10-25

Packages (OSV)

References

• https://github.com/copier-org/copier/releases/tag/v9.15.2
• https://github.com/copier-org/copier/security/advisories/GHSA-9gmc-jqmh-3rvm
• https://github.com/copier-org/copier/security/advisories/GHSA-9gmc-jqmh-3rvm

Check your stackJSON