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Vulnerability record · CVE-2021-32837 · published 17 January 2023

CVE-2021-32837: Mechanize project mechanize inefficient regular expression (redos) vulnerability

Mechanize Project · Mechanize

mechanize, a library for automatically interacting with HTTP web servers, contains a regular expression that is vulnerable to regular expression denial of service (ReDoS) prior to version 0.4.6. If a web server responds in a malicious way, then mechanize could crash. Version 0.4.6 has a patch for the issue.

7.5 CVSS 3.1 High EPSS 29% · top 1.9% CWE-1333 · Inefficient regular expression (ReDoS)
7.5CVSS 3.1 base score
29%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
11References, 4 tagged exploit
17 Jun 2026Last modified by NVD

Description

mechanize, a library for automatically interacting with HTTP web servers, contains a regular expression that is vulnerable to regular expression denial of service (ReDoS) prior to version 0.4.6. If a web server responds in a malicious way, then mechanize could crash. Version 0.4.6 has a patch for the issue.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L ExploitThird Party Advisory
https://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6 PatchThird Party Advisory
https://github.com/python-mechanize/mechanize/releases/tag/v0.4.6 Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/ ExploitThird Party Advisory
https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L ExploitThird Party Advisory
https://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6 PatchThird Party Advisory
https://github.com/python-mechanize/mechanize/releases/tag/v0.4.6 Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
https://lists.debian.org/debian-lts-announce/2025/12/msg00028.html
https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/ ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-32837), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.