CVE-2026-126190
Published:November 12, 2026
Updated:November 13, 2026
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 4.0, Soup Sieve repeatedly walks the same ancestors while matching descendant combinators, and each additional descendant combinator raises the polynomial degree of the work on deeply nested attacker-influenced HTML or XML. Applications using selectors such as section div div through select(), select_one(), or Beautiful Soup CSS APIs against untrusted documents can have a worker occupied for seconds or minutes, while trusted-only document processing is not affected. Selectors compiled with NOCACHE continue to use the old uncached behavior. This issue is fixed in version 4.0.
Affected Packages
soupsieve (CONDA):
Affected version(s) >=3.0 <4.0 || >=2.0.1 <4.0 || >=1.6.2 <4.0Fix Suggestion:
Update to version 4.0https://github.com/facelessuser/soupsieve.git (GITHUB):
Affected version(s) >=0.4.0 <4.0 || >=1.0.0b1 <4.0 || >=2.0.0 <4.0 || >=3.0 <4.0Fix Suggestion:
Update to version 4.0soupsieve (PYTHON):
Affected version(s) >=2.0 <4.0 || >=3.0 <4.0 || >=1.0b1 <4.0 || >=0.4 <4.0Fix Suggestion:
Update to version 4.0Related Resources (7)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Inefficient Algorithmic Complexity
EPSS
Base Score:
0.54