{"cvss":8.9,"datePublished":"2025-12-05T16:15:51.053","dateUpdated":"2026-09-25T23:10:00.463","description":"urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0.","id":"CVE-2025-66418","raw":{"affected":[{"affectedData":[{"product":"urllib3","vendor":"urllib3","versions":[{"status":"affected","version":">= 1.24, < 2.6.0"}]}],"source":"security-advisories@github.com"}],"configurations":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:*","matchCriteriaId":"AE1F753E-4D9D-48B1-B893-B3FD39917478","versionEndExcluding":"2.6.0","versionStartIncluding":"1.24","vulnerable":true}],"negate":false,"operator":"OR"}]}],"cveTags":[],"descriptions":[{"lang":"en","value":"urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0."},{"lang":"es","value":"urllib3 es una biblioteca cliente HTTP fácil de usar para Python. A partir de la versión 1.24 y en versiones anteriores a la 2.6.0, el número de enlaces en la cadena de descompresión era ilimitado, lo que permitía a un servidor malicioso insertar un número prácticamente ilimitado de pasos de compresión, lo que provocaba un alto uso de CPU y una asignación masiva de memoria para los datos descomprimidos. Esta vulnerabilidad se corrigió en la versión 2.6.0."}],"id":"CVE-2025-66418","lastModified":"2026-09-25T23:10:00.463","metrics":{"cvssMetricV31":[{"cvssData":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"exploitabilityScore":3.9,"impactScore":3.6,"source":"nvd@nist.gov","type":"Primary"}],"cvssMetricV40":[{"cvssData":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","availabilityRequirement":"NOT_DEFINED","baseScore":8.9,"baseSeverity":"HIGH","confidentialityRequirement":"NOT_DEFINED","exploitMaturity":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"source":"security-advisories@github.com","type":"Secondary"}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"id":"CVE-2025-66418","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","timestamp":"2025-12-05T16:15:39.701596Z","version":"2.0.3"}}]},"published":"2025-12-05T16:15:51.053","references":[{"source":"security-advisories@github.com","tags":["Patch"],"url":"https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8"},{"source":"security-advisories@github.com","tags":["Vendor Advisory"],"url":"https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53"}],"sourceIdentifier":"security-advisories@github.com","vulnStatus":"Analyzed","weaknesses":[{"description":[{"lang":"en","value":"CWE-770"}],"source":"security-advisories@github.com","type":"Secondary"}]},"severity":"HIGH","source":"nvd","title":"urllib3 is a user-friendly HTTP client library for Python"}