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TI-2026-19328 Aliases CVE-2026-23986GHSA-4fqp-r85r-hxqh

Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true

Priority LOW 32CWE-61Published · Updated

Key facts

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

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.

Summary

Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently write to arbitrary directories outside the destination path by using directory a symlink along with `_preserve_symlinks: true` and a generated directory structure whose rendered path is inside the symlinked directory. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc. Version 9.11.2 patches the issue.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0027 19th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed copier (copier-org): 9.11.2copier (PyPI): 9.11.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
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

VendorProductAffected versionsFixed inStatusSource
copier-orgcopierbefore 9.11.29.11.2Patch availableCNA
—copier (PyPI)before 9.11.29.11.2Patch availableGHSA-4fqp-r85r-hxqh
  • copier Vendorcopier-org Affected before 9.11.2 Fixed in 9.11.2 Patch available CNA
  • copier (PyPI) Vendor— Affected before 9.11.2 Fixed in 9.11.2 Patch available GHSA-4fqp-r85r-hxqh

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:copier-org:copier:*:*:*:*:*:python:*:*before 9.11.2Vulnerablecopier-org
  • cpe:2.3:a:copier-org:copier:*:*:*:*:*:python:*:* Versions before 9.11.2 Vulnerable ·copier-org

Remediation

  • Fix · CNA copier (copier-org) Fixed in 9.11.2
  • Fix · GHSA-4fqp-r85r-hxqh copier (PyPI) Fixed in 9.11.2 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-23986
  2. 2026-10-03 Alias added: GHSA-4fqp-r85r-hxqh

References

Exploit 1

Patch 1

Advisory 1

Other 2

  • 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-2026-19310 Copier safe template has arbitrary filesystem read access via symlinks when _preserve_symlinks: false CVSS 4.0MEDIUM 6.8

Sources

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