CVE-2026-23968 — copier
Fix: copier-org/copier@b3a7b37CVE-2026-23968 is a CWE-61 vulnerability in copier. A fix is available for copier — see the affected versions and patch details below.
Copier safe template has arbitrary filesystem read access via symlinks when _preserve_symlinks: false
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-23968.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
copierReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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 include arbitrary files/directories outside the local template clone location by using symlinks along with _preserve_symlinks: false (which is Copier's default setting).
Imagine, e.g., a malicious template author who creates a template that reads SSH keys or other secrets from well-known locations and hopes for a user to push the generated project to a public location like github.com where the template author can extract the secrets.
Reproducible example:
-
Illegally include a file in the generated project via symlink resolution:
echo "s3cr3t" > secret.txt mkdir src/ pushd src/ ln -s ../secret.txt stolen-secret.txt popd uvx copier copy src/ dst/ cat dst/stolen-secret.txt #s3cr3t -
Illegally include a directory in the generated project via symlink resolution:
mkdir secrets/ pushd secrets/ echo "s3cr3t" > secret.txt popd mkdir src/ pushd src/ ln -s ../secrets stolen-secrets popd uvx copier copy src/ dst/ tree dst/ # dst/ # └── stolen-secrets # └── secret.txt # # 1 directory, 1 file cat dst/stolen-secrets/secret.txt # s3cr3t
Patches
n/a
Workarounds
n/a
References
n/a
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | copier | all versions | 9.11.2pip install --upgrade 'copier==9.11.2' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for copier, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update copier to 9.11.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23968 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-23968 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-23968. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-23968 in your dependencies?
O3 Security finds CVE-2026-23968 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.