Arbitrary file disclosure via unrestricted getfile path
Published May 20, 2021 · Updated Dec 18, 2025
Path traversal in CPython's pydoc before 3.8.9, 3.9.3, and 3.10.0a7 allows local users to read arbitrary files. The html_getfile handler URL-decodes the supplied getfile key and passes the resulting path directly to tokenize.open without restricting it to an allowed directory. Exploitation requires another user to start a reachable pydoc server; access is limited to files readable by that server process, including from an adjacent network when exposed.
Summary
What happened
Path traversal in CPython's pydoc before 3.8.9, 3.9.3, and 3.10.0a7 allows local users to read arbitrary files. The html_getfile handler URL-decodes the supplied getfile key and passes the resulting path directly to tokenize.open without restricting it to an allowed directory. Exploitation requires another user to start a reachable pydoc server; access is limited to files readable by that server process, including from an adjacent network when exposed.
The record
- CVE
- CVE-2021-3426
- Published
- May 20, 2021
- Updated
- Dec 18, 2025
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-22, CWE-200, T1005
- Attack vector
- adjacent
- Privileges
- authenticated
Timeline
How it unfolded
- May 20, 2021CVE publishedPublication date reported by the CVE source.
- Dec 18, 2025Record 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=python 3.8.9, python 3.9.3, python 3.10.0a7
What conditions does exploitation require?
What is affected?
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
- pydoc getfile arbitrary-file-read reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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