{"id":"CVE-2026-34230","state":"PUBLISHED","title":"Rack: Quadratic complexity in Rack::Utils.select_best_encoding via wildcard Accept-Encoding header","description":"Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.","publishedAt":"2026-04-02T16:41:21.095Z","updatedAt":"2026-04-03T18:19:00.388Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["rack rack"],"affected":[{"vendor":"rack","product":"rack","versions":[{"version":"< 2.2.23","status":"affected"},{"version":">= 3.0.0.beta1, < 3.1.21","status":"affected"},{"version":">= 3.2.0, < 3.2.6","status":"affected"}]}],"references":["https://github.com/rack/rack/security/advisories/GHSA-v569-hp3g-36wr"],"weaknesses":["CWE-400","CWE-407"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/34xxx/CVE-2026-34230.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-34230","state":"PUBLISHED","datePublished":"2026-04-02T16:41:21.095Z","dateUpdated":"2026-04-03T18:19:00.388Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-26T16:22:29.034Z"},"containers":{"cna":{"title":"Rack: Quadratic complexity in Rack::Utils.select_best_encoding via wildcard Accept-Encoding header","descriptions":[{"lang":"en","value":"Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6."}],"affected":[{"vendor":"rack","product":"rack","versions":[{"version":"< 2.2.23","status":"affected"},{"version":">= 3.0.0.beta1, < 3.1.21","status":"affected"},{"version":">= 3.2.0, < 3.2.6","status":"affected"}]}],"references":[{"url":"https://github.com/rack/rack/security/advisories/GHSA-v569-hp3g-36wr","name":"https://github.com/rack/rack/security/advisories/GHSA-v569-hp3g-36wr","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM","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:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-407","lang":"en","description":"CWE-407: Inefficient Algorithmic Complexity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-02T16:41:21.095Z"},"source":{"advisory":"GHSA-v569-hp3g-36wr","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-02T18:56:03.220311Z","id":"CVE-2026-34230","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-03T18:19:00.388Z"}}]}}}