Vulnerability Details CVE-2026-49477
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminated quoted value in soupsieve/css_parser.py, allowing an attacker who can supply untrusted CSS selector strings to soupsieve.compile() or Beautiful Soup .select() / .select_one() to cause CPU exhaustion and denial of service. This issue is fixed in version 2.8.4.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.005
EPSS Ranking 41.9%
CVSS Severity
CVSS v3 Score 7.5
References
- https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3
- https://github.com/facelessuser/soupsieve/releases/tag/2.8.4
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37
Products affected by CVE-2026-49477
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cpe:2.3:a:facelessuser:soup_sieve:0.4.0
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cpe:2.3:a:facelessuser:soup_sieve:0.5.0
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cpe:2.3:a:facelessuser:soup_sieve:0.5.1
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cpe:2.3:a:facelessuser:soup_sieve:0.5.2
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cpe:2.3:a:facelessuser:soup_sieve:0.5.3
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cpe:2.3:a:facelessuser:soup_sieve:0.6.0
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cpe:2.3:a:facelessuser:soup_sieve:1.0.0
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cpe:2.3:a:facelessuser:soup_sieve:1.0.1
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cpe:2.3:a:facelessuser:soup_sieve:1.0.2
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cpe:2.3:a:facelessuser:soup_sieve:1.1.0
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cpe:2.3:a:facelessuser:soup_sieve:1.2.0
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cpe:2.3:a:facelessuser:soup_sieve:1.2.1
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cpe:2.3:a:facelessuser:soup_sieve:1.3.0
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cpe:2.3:a:facelessuser:soup_sieve:1.3.1
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cpe:2.3:a:facelessuser:soup_sieve:1.4.0
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cpe:2.3:a:facelessuser:soup_sieve:1.5.0
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cpe:2.3:a:facelessuser:soup_sieve:1.6.0
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cpe:2.3:a:facelessuser:soup_sieve:1.6.1
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cpe:2.3:a:facelessuser:soup_sieve:1.6.2
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cpe:2.3:a:facelessuser:soup_sieve:1.7.0
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cpe:2.3:a:facelessuser:soup_sieve:1.7.1
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cpe:2.3:a:facelessuser:soup_sieve:1.7.2
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cpe:2.3:a:facelessuser:soup_sieve:1.7.3
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cpe:2.3:a:facelessuser:soup_sieve:1.8.0
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cpe:2.3:a:facelessuser:soup_sieve:1.9.0
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cpe:2.3:a:facelessuser:soup_sieve:1.9.1
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cpe:2.3:a:facelessuser:soup_sieve:1.9.2
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cpe:2.3:a:facelessuser:soup_sieve:1.9.3
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cpe:2.3:a:facelessuser:soup_sieve:1.9.4
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cpe:2.3:a:facelessuser:soup_sieve:1.9.5
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cpe:2.3:a:facelessuser:soup_sieve:1.9.6
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cpe:2.3:a:facelessuser:soup_sieve:2.0.0
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cpe:2.3:a:facelessuser:soup_sieve:2.0.1
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cpe:2.3:a:facelessuser:soup_sieve:2.1.0
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cpe:2.3:a:facelessuser:soup_sieve:2.2
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cpe:2.3:a:facelessuser:soup_sieve:2.2.1
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cpe:2.3:a:facelessuser:soup_sieve:2.3
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cpe:2.3:a:facelessuser:soup_sieve:2.3.1
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cpe:2.3:a:facelessuser:soup_sieve:2.3.2
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cpe:2.3:a:facelessuser:soup_sieve:2.3.2.
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cpe:2.3:a:facelessuser:soup_sieve:2.4
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cpe:2.3:a:facelessuser:soup_sieve:2.4.1
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cpe:2.3:a:facelessuser:soup_sieve:2.5
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cpe:2.3:a:facelessuser:soup_sieve:2.6
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cpe:2.3:a:facelessuser:soup_sieve:2.7
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cpe:2.3:a:facelessuser:soup_sieve:2.8
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cpe:2.3:a:facelessuser:soup_sieve:2.8.1
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cpe:2.3:a:facelessuser:soup_sieve:2.8.2
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cpe:2.3:a:facelessuser:soup_sieve:2.8.3