Arbitrary file write via backslash path traversal
Published Jan 26, 2026 · Updated Jan 26, 2026
Path traversal in pnpm before 10.28.1 allows remote attackers to write outside package directories on Windows via malicious tarballs. The parseTarball function in store/cafs/src/parseTarball.ts normalizes entries containing ./ but fails to treat backslash-based traversal segments as directory traversal. Exploitation requires a Windows user or CI job to install an attacker-controlled package; the resulting file write can overwrite .npmrc or build configuration files.
Summary
What happened
Path traversal in pnpm before 10.28.1 allows remote attackers to write outside package directories on Windows via malicious tarballs. The parseTarball function in store/cafs/src/parseTarball.ts normalizes entries containing ./ but fails to treat backslash-based traversal segments as directory traversal. Exploitation requires a Windows user or CI job to install an attacker-controlled package; the resulting file write can overwrite .npmrc or build configuration files.
The record
- CVE
- CVE-2026-23889
- Published
- Jan 26, 2026
- Updated
- Jan 26, 2026
- Vendor
- pnpm
- Product
- pnpm
- Classifications
- CWE-22, T1195.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 26, 2026CVE publishedPublication date reported by the CVE source.
- Jan 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 10.28.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream malicious-tarball proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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