Recursive Parsing Vulnerability in Soup Sieve CSS Selector Library by Faceless User

CVE-2026-126193

What is CVE-2026-126193?

The Soup Sieve CSS selector library is vulnerable to a recursive parsing issue, where deeply nested CSS pseudo-class selectors can lead to exceeding Python's recursion limit, resulting in a RecursionError. This affects applications that process untrusted CSS selectors if exception handling is not implemented. While this does not result in an interpreter crash or persistent denial of service, it can cause specific requests or tasks to fail. Users are advised to upgrade to version 3.0, which addresses this vulnerability.

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