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.
CVE-2021-32837
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 1.9%, top 16% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 97.9%
- KEV
- Not listed
Published
January 17, 2023
Last Modified
December 22, 2025
References (11)
- security-advisories@githubhttps://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L878-L879
- security-advisories@githubhttps://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6
- security-advisories@githubhttps://github.com/python-mechanize/mechanize/releases/tag/v0.4.6
- security-advisories@githubhttps://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
- security-advisories@githubhttps://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/
- af854a3a-2127-422b-91ae-364da2661108https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L878-L879
- af854a3a-2127-422b-91ae-364da2661108https://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6
- af854a3a-2127-422b-91ae-364da2661108https://github.com/python-mechanize/mechanize/releases/tag/v0.4.6
- af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
- af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/12/msg00028.html
- af854a3a-2127-422b-91ae-364da2661108https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| mechanize | 0.0.10a ... v0.3.0 (50 versions) | 0.4.6 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 5× in last 7d / 39× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-11 08:25 UTCEPSS rescore
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- 2026-06-10 18:47 UTCOSV refresh
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- 2026-05-26 07:17 UTCEPSS rescore
- 2026-05-25 08:28 UTCEG score recompute
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2021-32837?
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Dependency Blast Radius
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