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Vulnerability record · CVE-2026-49477 · published 14 July 2026

CVE-2026-49477: Facelessuser soup sieve uncontrolled resource consumption vulnerability

FFacelessuser · Soup Sieve

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.

7.5 CVSS 3.1 High EPSS 0.64% · top 51.2% CWE-400 · Uncontrolled resource consumptionCWE-1333 · Inefficient regular expression (ReDoS)
7.5CVSS 3.1 base score
0.64%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
28 Jul 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3 Patch
https://github.com/facelessuser/soupsieve/releases/tag/2.8.4 Release Notes
https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 ExploitVendor Advisory
https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 ExploitVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-49477), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.