CVE-2026-49477: Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser
Vulnerability summary
CVE-2026-49477 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in facelessuser soup_sieve. EPSS estimates a 0.64% chance of exploitation in the next 30 days, higher than 50.9% of scored vulnerabilities. 1 public exploit is recorded.
Public exploit (GitHub, Date unknown)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 6 · Related 5Timeline
- 14-07-2026PublishedVulnerability first disclosed.
- 21-07-2026Last modifiedVulnerability information updated.
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 metrics
7 scores · 7 sources · 1 version- OSV · PypiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.64%
Chance of exploitation in the next 30 days
Percentile
51%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.64% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundSoupsieve
Maturity: poc
Weaknesses
CWE · root cause- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
- CWE-1333Inefficient Regular Expression ComplexityThe product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard22 products
- airflow-2< 2.11.2-r22
- datadog-agent-7.71-core-integrations< 7.71.2-r31
- datadog-agent-7.72-core-integrations< 7.72.4-r33
- datadog-agent-7.73-core-integrations< 7.73.3-r23
- datadog-agent-7.74-core-integrations< 7.74.1-r23
Wolfi11 products
- datadog-agent-7.72-core-integrations< 7.72.4-r33
- datadog-agent-7.73-core-integrations< 7.73.3-r23
- datadog-agent-7.74-core-integrations< 7.74.1-r23
- datadog-agent-7.75-core-integrationsAll versions (No fix recorded)
- datadog-agent-7.76< 7.76.3-r41
Facelessuser2 products
- soup_sieve< 2.8.4
- soupsieve< 2.8.4
Debian1 product
- soupsieveAll versions (No fix recorded) | < 2.8.4-1
PyPI1 product
- soupsieve< 2.8.4
Ubuntu1 product
- soupsieveAll versions (No fix recorded)
6 vendors · 38 products
References
11 links- github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37X Refsource CONFIRMWEBREPORTAdvisoryExploitVendor Advisory
- github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3X Refsource MISCREPORTFIXPatch
- pypi.org/project/soupsievePACKAGE
