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Fencer Vulns
high 7.5

CVE-2021-32837 in the critical feed json

mechanize vulnerable to ReDoS

published 2023-01-17 3 y ago modified 2026-06-17 4 mo ago also GHSA-g3pv-pj5f-3hfq , PYSEC-2023-25 , EUVD-2023-0144

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
28.7%
EPSS 28.7% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi mechanize 0.4.6
  • mechanize_project mechanize 0.4.6
  • python-mechanize Debian 14, Debian 13, Debian 12 1:0.4.7-1

debian advisories DEBIAN-CVE-2021-32837

  • python-mechanize openSUSE Tumbleweed 0.4.10-1.4
  • python-mechanize Package Hub 15 SP4, openSUSE Leap 15.4 0.4.8-bp154.2.3.1

opensuse advisories openSUSE-SU-2025:15098-1openSUSE-SU-2023:0030-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-32837 updated cvss 7.5

mechanize: Regular Expression Denial of Service

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

28.66% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • securitylab.github.com https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/ referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L878-L879 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi mechanize
<0.4.6
0.4.6

Affected products

  • python-mechanize mechanize

Classification

Weakness
  • CWE-1333 Inefficient Regular Expression Complexity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.