CVE-2025-6069: 
Python Interpreter vulnerability analysis and mitigation

CVE-2025-6069 affects the html.parser.HTMLParser class in Python's standard library, discovered and disclosed on June 13, 2025. The vulnerability involves a worst-case quadratic complexity issue when processing certain crafted malformed HTML inputs. The Python Software Foundation assigned it a CVSS v3.1 base score of 4.3 (MEDIUM) (Wiz Report, Python CVE).

The vulnerability exists in the HTMLParser class when processing malformed HTML inputs, where the parser's behavior could lead to excessive processing time. The CVSS vector string is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L, indicating network accessibility with low attack complexity and privileged access required. Test cases that previously took about an hour to process now take a fraction of a second after the fix, demonstrating the significant performance impact of the vulnerability (Python Issue, Python PR).

The vulnerability can potentially lead to amplified denial-of-service conditions. The processing time difference between patched and unpatched versions is significant, with test cases showing a reduction from approximately one hour to a fraction of a second after applying the fix (Wiz Report).

The issue has been fixed in multiple Python versions through a series of patches. The fix has been backported to Python versions 3.9 through 3.14. Users should update to the patched versions of Python to mitigate this vulnerability (Python Commits).