CVE-2026-53951
HIGH
MEDIUM
Priority: 0.02
BB Relevance:
43/100
Published: 2026-07-08
Modified: 2026-10-25
First seen: 2026-10-29
Status: active
Attack Surface
Low Complexity
No Auth
Conf. Impact
Integ. Impact
CVSS Vector Breakdown
AV:
Local
AC:
Low
PR:
None
UI:
Passive
S:
X
AT:
Present
VC:
High
VI:
High
VA:
High
Description
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.