Arbitrary file write via drive-prefixed ZIP paths
Published Apr 27, 2026 · Updated Apr 27, 2026
Path traversal in CPython's shutil module allows attackers to write files outside the extraction directory on Windows via a crafted ZIP. The _unpack_zipfile() helper rejects slash-prefixed and dot-dot names but joins drive-prefixed member names to extract_dir without rejecting or sanitizing them. Exploitation requires an application to pass an attacker-controlled ZIP to shutil.unpack_archive(); the flaw affects the 3.10 through 3.15 branches and writes with the process account's permissions.
Summary
What happened
Path traversal in CPython's shutil module allows attackers to write files outside the extraction directory on Windows via a crafted ZIP. The _unpack_zipfile() helper rejects slash-prefixed and dot-dot names but joins drive-prefixed member names to extract_dir without rejecting or sanitizing them. Exploitation requires an application to pass an attacker-controlled ZIP to shutil.unpack_archive(); the flaw affects the 3.10 through 3.15 branches and writes with the process account's permissions.
The record
- CVE
- CVE-2026-3087
- Published
- Apr 27, 2026
- Updated
- Apr 27, 2026
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-22
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 27, 2026CVE publishedPublication date reported by the CVE source.
- Apr 27, 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?
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- Affected versionversion=0
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
- Minimal shutil drive-prefixed ZIP reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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