CVE-2026-49477Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser
- 7.5HighCVSS base score
- 0.64%Exploitation in 30 daysEPSS · top 49% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 45 days later
· 45 days later
Published
- 7 days later
· 7 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.64% · top 49% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
- affected < 2.8.4
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIsoupsieveGHSA-836r-79rf-4m37 (opens in a new tab)
References
References3
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37 (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3 (opens in a new tab)x_refsource_MISC
- https://github.com/facelessuser/soupsieve/releases/tag/2.8.4 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-44538 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-836r-79rf-4m37 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-49477)Record last updated .