CVE-2026-126191
Published:November 12, 2026
Updated:November 14, 2026
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 3.0, the CSS_ESCAPES and IDENTIFIER regular-expression subpatterns can backtrack exponentially on runs of ambiguous digit escapes in an attribute-name or tag position of an otherwise valid selector. The failure occurs during selector compilation through soupsieve.compile() or Beautiful Soup select() before SELECTOR_LIMIT is applied, so an application that accepts untrusted selector strings can have a worker stalled by a short input. This issue is fixed in version 3.0.
Affected Packages
soupsieve (CONDA):
Affected version(s) >=2.0.1 <3.0 || >=1.6.2 <3.0Fix Suggestion:
Update to version 3.0https://github.com/facelessuser/soupsieve.git (GITHUB):
Affected version(s) >=0.4.0 <3.0 || >=1.0.0b1 <3.0 || >=2.0.0 <3.0Fix Suggestion:
Update to version 3.0soupsieve (PYTHON):
Affected version(s) >=1.0b1 <3.0 || >=0.4 <3.0 || >=2.0 <3.0Fix Suggestion:
Update to version 3.0Related 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 Regular Expression Complexity
EPSS
Base Score:
0.43