TI-2026-38919 Aliases CVE-2026-53951 GHSA-9gmc-jqmh-3rvm

Copier: trust-prefix bypass via path traversal runs tasks unprompted

HIGH 73CWE-22Published 2026-07-08 · Updated 2026-07-09

Key facts

Attack vector: Local
Privileges required: None
User interaction: Passive
Attack complexity: Low
Attack requirements: Present
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-94.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00261 17th percentileScored 2026-11-07

Fix Fixed copier (copier-org): 9.15.2copier (PyPI): 9.15.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
copier-org	copier	9.5.0 to before 9.15.2	9.15.2	Patch available	CNA
—	copier (PyPI)	9.5.0 to before 9.15.2	9.15.2	Patch available	GHSA-9gmc-jqmh-3rvm

copier Vendorcopier-org Affected 9.5.0 to before 9.15.2 Fixed in 9.15.2 Patch available CNA
copier (PyPI) Vendor— Affected 9.5.0 to before 9.15.2 Fixed in 9.15.2 Patch available GHSA-9gmc-jqmh-3rvm

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:copier-org:copier::::::::	—	—	copier-org

cpe:2.3:a:copier-org:copier:*:*:*:*:*:*:*:* Versions — — ·copier-org

Remediation

Fix · CNA copier (copier-org) Fixed in 9.15.2
Fix · GHSA-9gmc-jqmh-3rvm copier (PyPI) Fixed in 9.15.2 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-53951
2026-10-03 Alias added: GHSA-9gmc-jqmh-3rvm

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-53951

Other 3

TI-2025-34877 Copier safe template has arbitrary filesystem read/write access CVSS 4.0HIGH 8.5
TI-2026-45000 Path traversal in copier-org copier CVSS 3.1HIGH 7.5
TI-2025-34889 Copier safe template has filesystem write access outside destination path CVSS 4.0MEDIUM 6.9
TI-2026-26974 Copier `_external_data` allows path traversal and absolute-path local file read without unsafe mode CVSS 3.1MEDIUM 5.5
TI-2026-26970 Copier `_subdirectory` allows template root escape via parent-directory traversal CVSS 3.1MEDIUM 4.4
TI-2026-19328 Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true CVSS 4.0MEDIUM 6.9

See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences