Copier's safe template has arbitrary filesystem read/write access

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.5 · CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2025-55201: 0.26% estimated exploitation activity in the next 30 days; percentile 17.72 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Copier's current security model shall restrict filesystem access through Jinja: - Files can only be read using {% include ... %}, which is limited by Jinja to reading files from the subtree of the local template clone in our case. - Files are written in the destination directory according to their counterparts in the template. 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 read and write arbitrary files because we expose a few pathlib.Path objects in the Jinja context which have unconstrained I/O methods. This effectively renders our security model w.r.t. filesystem access useless. Arbitrary read access Imagine, e.g., a malicious template author who creates a template that reads SSH keys or other secrets from well-known locations, perhaps "masks" them with Base64 encoding to…

Published by the source

18 Aug 2025, 21:00 UTC

Last modified by the source

7 Jul 2026, 17:57 UTC

Source last checked

26 Oct 2026, 13:32 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3xw7-v6cj-5q8h

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3xw7-v6cj-5q8h

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# Patch Next advisory brief: CVE-2025-55201

Advisory: Copier's safe template has arbitrary filesystem read/write access
IDs: CVE-2025-55201, GHSA-3xw7-v6cj-5q8h
Record: https://patchnext.com/advisories/cve-2025-55201 (revision 3, source checked 26 Oct 2026, 13:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: copier 9.9.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI copier: affected < 9.9.1; fixed in 9.9.1

## Suggested inspection (read-only)
- `python -m pip show copier`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on copier.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3xw7-v6cj-5q8h (OSV record GHSA-3xw7-v6cj-5q8h lists affected ranges: PyPI copier >=0 <9.9.1 (fixed))
- Verified: https://github.com/advisories/GHSA-3xw7-v6cj-5q8h (GitHub-reviewed advisory GHSA-3xw7-v6cj-5q8h lists affected ranges: PyPI copier >=0 <9.9.1)

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