# CVE-2026-23986: Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true

> A malicious template can overwrite arbitrary files outside the destination directory via symlink traversal when symlink preservation is enabled.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Jan 2026
- **Updated:** 22 Jan 2026
- **Also known as:** GHSA-4fqp-r85r-hxqh, PYSEC-2026-1272

## What is CVE-2026-23986?

CVE-2026-23986 is a medium-severity path traversal vulnerability in copier-org copier, published on 21 Jan 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-61 (UNIX Symbolic Link (Symlink) Following)

## Which versions are affected by CVE-2026-23986?

3 open source packages ship an affected version, including copier. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `copier` | PyPI | All versions | 9.11.2 |
| `copier` | PyPI | All versions | 9.11.2 |
| `copier` | PyPI | All versions | 9.11.2 |

Products: Copier-Org Copier.

## How do I fix CVE-2026-23986?

Upgrade copier to 9.11.2 or later.

## Is CVE-2026-23986 being exploited?

There is no known exploitation of CVE-2026-23986 in the wild and no public exploit code.

## Other vulnerabilities in copier-org copier

- [CVE-2026-23968](https://insights.sbomify.com/CVE-2026-23968/): Copier safe template has arbitrary filesystem read access via symlinks when _preserve_symlinks: false (medium 6.8)
- [CVE-2026-34730](https://insights.sbomify.com/CVE-2026-34730/): Copier `_external_data` allows path traversal and absolute-path local file read without unsafe mode (medium 5.5)
- [CVE-2026-34726](https://insights.sbomify.com/CVE-2026-34726/): Copier `_subdirectory` allows template root escape via parent-directory traversal (medium 4.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23986 and fix it if it is affected.

What it is: CVE-2026-23986 is a medium-severity path traversal vulnerability in copier-org copier, published on 21 Jan 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-23986 in the wild and no public exploit code.

Affected packages and fixed versions:
- copier (PyPI): affected all versions; fixed in 9.11.2
- copier (PyPI): affected all versions; fixed in 9.11.2
- copier (PyPI): affected all versions; fixed in 9.11.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-23986/ (Markdown: https://insights.sbomify.com/CVE-2026-23986/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23986
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23986
- OSV: https://osv.dev/vulnerability/CVE-2026-23986

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23986/
Summaries are generated and may contain mistakes; the official description above is the record.