{"id":"CVE-2026-27601","state":"PUBLISHED","title":"Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack","description":"Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be exploited if there exists a code path in which two distinct datastructures that were submitted by the same remote client are compared using _.isEqual. For example, if a client submits data that are stored in a database, and the same client can later submit another datastructure that is then compared to the data that were saved in the database previously, OR if a client submits a single request, but its data are parsed twice, creating two non-identical but equivalent datastructures that are then compared. Exceptions originating from the call to _.flatten or _.isEqual, as a result of a stack overflow, are not being caught. This vulnerability is fixed in 1.13.8.","publishedAt":"2026-03-03T22:38:38.955Z","updatedAt":"2026-03-04T16:44:40.856Z","severity":{"score":8.2,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["jashkenas underscore"],"affected":[{"vendor":"jashkenas","product":"underscore","versions":[{"version":"< 1.13.8","status":"affected"}]}],"references":["https://github.com/jashkenas/underscore/security/advisories/GHSA-qpx9-hpmf-5gmw","https://github.com/jashkenas/underscore/commit/411e222eb0ca5d570cc4f6315c02c05b830ed2b4","https://github.com/jashkenas/underscore/commit/a6e23ae9647461ec33ad9f92a2ecfc220eea0a84"],"weaknesses":["CWE-770"],"ingestedAt":"2026-10-29T20:11:31.369Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/27xxx/CVE-2026-27601.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-27601","state":"PUBLISHED","datePublished":"2026-03-03T22:38:38.955Z","dateUpdated":"2026-03-04T16:44:40.856Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-02-20T19:43:14.602Z"},"containers":{"cna":{"title":"Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack","descriptions":[{"lang":"en","value":"Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be exploited if there exists a code path in which two distinct datastructures that were submitted by the same remote client are compared using _.isEqual. For example, if a client submits data that are stored in a database, and the same client can later submit another datastructure that is then compared to the data that were saved in the database previously, OR if a client submits a single request, but its data are parsed twice, creating two non-identical but equivalent datastructures that are then compared. Exceptions originating from the call to _.flatten or _.isEqual, as a result of a stack overflow, are not being caught. This vulnerability is fixed in 1.13.8."}],"affected":[{"vendor":"jashkenas","product":"underscore","versions":[{"version":"< 1.13.8","status":"affected"}]}],"references":[{"url":"https://github.com/jashkenas/underscore/security/advisories/GHSA-qpx9-hpmf-5gmw","name":"https://github.com/jashkenas/underscore/security/advisories/GHSA-qpx9-hpmf-5gmw","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/jashkenas/underscore/commit/411e222eb0ca5d570cc4f6315c02c05b830ed2b4","name":"https://github.com/jashkenas/underscore/commit/411e222eb0ca5d570cc4f6315c02c05b830ed2b4","tags":["x_refsource_MISC"]},{"url":"https://github.com/jashkenas/underscore/commit/a6e23ae9647461ec33ad9f92a2ecfc220eea0a84","name":"https://github.com/jashkenas/underscore/commit/a6e23ae9647461ec33ad9f92a2ecfc220eea0a84","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.2,"baseSeverity":"HIGH","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:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-770","lang":"en","description":"CWE-770: Allocation of Resources Without Limits or Throttling","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-03T22:38:38.955Z"},"source":{"advisory":"GHSA-qpx9-hpmf-5gmw","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-04T16:44:25.481747Z","id":"CVE-2026-27601","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-04T16:44:40.856Z"}}]}}}