{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-34831","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-03-30T20:52:53.284Z","datePublished":"2026-04-02T16:43:08.762Z","dateUpdated":"2026-04-03T17:48:11.330Z"},"containers":{"cna":{"title":"Rack: Content-Length mismatch in Rack::Files error responses","problemTypes":[{"descriptions":[{"cweId":"CWE-130","lang":"en","description":"CWE-130: Improper Handling of Length Parameter Inconsistency","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-135","lang":"en","description":"CWE-135: Incorrect Calculation of Multi-Byte String Length","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.8,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/rack/rack/security/advisories/GHSA-q2ww-5357-x388","tags":["x_refsource_CONFIRM"],"url":"https://github.com/rack/rack/security/advisories/GHSA-q2ww-5357-x388"}],"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"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-04-02T16:43:08.762Z"},"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::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6."}],"source":{"advisory":"GHSA-q2ww-5357-x388","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-03T17:43:52.462237Z","id":"CVE-2026-34831","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-04-03T17:48:11.330Z"}}]}}