CVE-2026-23986 json
Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true
published 2026-01-21 9 mo ago modified 2026-07-07 4 mo ago also GHSA-4fqp-r85r-hxqh , PYSEC-2026-1272 , EUVD-2026-4141
- cvss
- 7.1
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 19%
- public exploits
- 0
- none known
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.
Patch / fix
- pypi copier 9.11.2
- copier-org copier 9.11.2
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 9 mo ago
Exploit prediction
0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/copier-org/copier/security/advisories/GHSA-4fqp-r85r-hxqh referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 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 |
| CNA | 4.0 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H |
| GitHub | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H |
| OSV | 3.1 | 7.1 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | copier | <9.11.2 |
9.11.2 |
Affected products
- copier-org copier
Classification
- Weakness
-
- CWE-61 UNIX Symbolic Link (Symlink) Following
References
-
github.com
/copier-org/copier/commit/b3a7b3772d17cf0e7a4481978188c9f536c8d8f6
web, patch
-
github.com
/copier-org/copier/security/advisories/GHSA-4fqp-r85r-hxqh
web, exploit, third-party-advisory
-
github.com
/copier-org/copier/releases/tag/v9.11.2
web, product, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-23986
advisory
-
github.com
/copier-org/copier
package
-
pypi.org
/project/copier
package
-
github.com
/advisories/GHSA-4fqp-r85r-hxqh
advisory
Sources
- CVE List CVE-2026-23986
- GitHub Advisory GHSA-4fqp-r85r-hxqh
- NVD CVE-2026-23986
- OSV PYSEC-2026-1272
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.