The vulnerability identified as CVE-2025-6069 involves inefficient regular expression complexity in the html.parser.HTMLParser class of CPython. When processing certain malformed inputs, the parser's algorithm exhibits quadratic time complexity, potentially allowing an attacker to cause a denial-of-service by amplifying resource consumption. This flaw is categorized under CWE-1333 (Inefficient Regular Expression Complexity). The affected versions explicitly include CPython 3.10.0, 3.11.0, 3.12.0, 3.13.0, 3.14.0, and 3.14.0a1. The CVSS v3.1 base score is 4.3, indicating medium severity, with network attack vector, low attack complexity, requiring low privileges, no user interaction, and impact limited to availability.

An attacker can exploit this vulnerability by supplying crafted malformed inputs to the html.parser.HTMLParser class, causing the parser to consume excessive CPU resources due to quadratic complexity in regular expression processing. This can lead to denial-of-service conditions by amplifying resource exhaustion. There is no impact on confidentiality or integrity.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided at this time. Until a patch is available, users should consider limiting exposure of services that parse untrusted HTML input or apply other application-level mitigations to reduce the risk of denial-of-service.