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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
facelessuser soupsieve affected
Version Status Constraints
< 2.8.4 affected —

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Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-836r-79rf-4m37 Soup Sieve: Regular Expression Denial of Service (ReDoS) via Selector Parser
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3 cve-icon
https://github.com/facelessuser/soupsieve/releases/tag/2.8.4 cve-icon
https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 cve-icon
History

Tue, 14 Jul 2026 21:15:00 +0000

Type Values Removed Values Added
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.
Title Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser
Weaknesses CWE-1333
CWE-400
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-14T20:51:29.369Z

Reserved: 2026-05-30T04:17:43.095Z

Link: CVE-2026-49477

cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses