Python URL Parser: Improper Input Validation in Python URL Parser (CVE-2025-0938) #shorts

Summary

Today, we're talking about CVE-2025-0938, a vulnerability affecting the Python standard library's URL parser functions. This issue revolves around improper input validation that could lead to unexpected behavior and possibly privilege escalation in certain Python applications.

Product details

The vulnerability impacts multiple versions of the Python programming language provided by the Python Software Foundation. Specifically, it affects CPython versions below 3.12.9, between 3.13.0 and 3.13.2, and versions preceding 3.14.0a4. This includes some common distributions like Fedora 40 and 41, and various SUSE Linux Enterprise releases.

Vulnerability type summary

The vulnerability is identified as CWE-20, which signifies Improper Input Validation. This type of flaw occurs when software does not properly validate input, allowing attackers to affect program execution through unexpected commands or inputs.

Details of the vulnerability

The problem lies in the Python standard library functions `urllib.parse.urlsplit` and `urlparse`. These functions accepted domain names with square brackets, which are only valid for IPv6 and IPvFuture host addresses according to RFC 3986. This mismatch in parsing can result in vulnerabilities such as privilege escalation, particularly when the URLs are processed differently by other specification-compliant parsers.

Conclusion

In conclusion, it's critical for developers and system administrators using affected versions of Python to update their systems promptly. Security advisories have already been released by Fedora and SUSE to address this issue. Ensuring your systems are using the latest patch will mitigate the risks associated with CVE-2025-0938.

This chain involves the following actors

This following systems are involved

Attack entry point

Remediation actions

Exploitation actions

• https://github.com/python/cpython/issues/105704
• https://github.com/python/cpython/pull/129418
• https://mail.python.org/archives/list/security-announce@python.org/thread/K4EUG6EKV6JYFIC24BASYOZS4M5XOQIB/
• https://github.com/python/cpython/commit/d89a5f6a6e65511a5f6e0618c4c30a7aa5aba56a
• https://github.com/python/cpython/commit/90e526ae67b172ed7c6c56e7edad36263b0f9403
• https://github.com/python/cpython/commit/a7084f6075c9595ba60119ce8c62f1496f50c568
• https://github.com/python/cpython/commit/526617ed68cde460236c973e5d0a8bad4de896ba
• https://github.com/python/cpython/commit/b8b4b713c5f8ec0958c7ef8d29d6711889bc94ab
• https://github.com/python/cpython/commit/ff4e5c25666f63544071a6b075ae8b25c98b7a32