CVE-2026-53951: high-severity vulnerability in copier-org copier
Copier: trust-prefix bypass via path traversal runs tasks unprompted
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.8epss 0.3%
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/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
Affected products
copier-org · copierRelated CVEs — copier-org copier
In the same product, most dangerous first.
CVE-2026-62999HIGHCopier: Percent-encoded dot segments in template URLs can allow trusted-prefix escape (Incomplete fix for trust-prefix bypass)EPSS 0.4%CVE-2026-34726MEDIUMCopier `_subdirectory` allows template root escape via parent-directory traversalEPSS 0.4%CVE-2026-34730MEDIUMCopier `_external_data` allows path traversal and absolute-path local file read without unsafe modeEPSS 0.3%CVE-2026-23986MEDIUMCopier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: trueEPSS 0.3%CVE-2025-55214MEDIUMCopier safe template has filesystem write access outside destination pathEPSS 0.3%CVE-2025-55201HIGHCopier safe template has arbitrary filesystem read/write accessEPSS 0.3%