CVE-2021-3426
CWE-200Published: May 20, 2021· Updated: Jun 17, 2026
Official Description
There's a flaw in Python 3's pydoc. A local or adjacent attacker who discovers or is able to convince another local or adjacent user to start a pydoc server could access the server and use it to disclose sensitive information belonging to the other user that they would not normally be able to access. The highest risk of this flaw is to data confidentiality. This flaw affects Python versions before 3.8.9, Python versions before 3.9.3 and Python versions before 3.10.0a7.
Technical Analysis
CVE-2021-3426 requires adjacent network access, limiting remote exploitation but still posing risk in shared or local network environments.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 5.7.
From a weakness classification perspective (CWE-200): Information exposure vulnerabilities leak sensitive data to unauthorized actors.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (29)
Quick Facts
Related CVEs (CWE-200)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-3426 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts