Resource exhaustion in Facelessuser Soup Sieve
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.
Vulnerability class: DoS (Denial of Service)
EPSS: 0.005 (42.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Facelessuser Soup_sieve
- Facelessuser Soupsieve — versions < 2.8.4
Weakness classification (CWE)
References
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-49477?
- CVE-2026-49477 is a high-severity vulnerability in Facelessuser Soup Sieve, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-07-14.
- How severe is CVE-2026-49477?
- High severity. CVSS v3 base score is 7.5 out of 10.