CVE-2021-32837

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.

Weakness

The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

Affected Software

Extended Description

	  Attackers can create crafted inputs that
	  intentionally cause the regular expression to use
	  excessive backtracking in a way that causes the CPU
	  consumption to spike.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/492.html

References

• https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L878-L879
• https://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6
• https://github.com/python-mechanize/mechanize/releases/tag/v0.4.6
• https://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
• https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/
• https://github.com/python-mechanize/mechanize/blob/3acb1836f3fd8edc5a758a417dd46b53832ae3b5/mechanize/_urllib2_fork.py#L878-L879
• https://github.com/python-mechanize/mechanize/commit/dd05334448e9f39814bab044d2eaa5ef69b410d6
• https://github.com/python-mechanize/mechanize/releases/tag/v0.4.6
• https://lists.debian.org/debian-lts-announce/2023/06/msg00022.html
• https://securitylab.github.com/advisories/GHSL-2021-108-python-mechanize-mechanize/