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{"bugzilla": {"description": "rack: Rack: HTTP response desynchronization via incorrect Content-Length calculation with UTF-8 characters", "id": "2454504", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2454504"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.8", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N", "status": "draft"}, "cwe": "CWE-135", "details": ["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.", "A flaw was found in Rack. A remote attacker can exploit this vulnerability by requesting a non-existent path containing percent-encoded UTF-8 characters. This causes Rack::Files#fail to incorrectly calculate the Content-Length header, using String#size instead of String#bytesize for multibyte characters. This leads to incorrect HTTP response framing, which may cause response desynchronization in systems relying on the Content-Length value."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-34831", "package_state": [{"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Fix deferred", "package_name": "openshift-logging/cluster-logging-operator-bundle", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Fix deferred", "package_name": "openshift-logging/cluster-logging-rhel9-operator", "product_name": "Logging Subsystem for Red Hat OpenShift"}, {"cpe": "cpe:/a:redhat:logging:5", "fix_state": "Fix deferred", "package_name": "openshift-logging/eventrouter-rhel9", "product_name": "Logging 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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.2.23)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.0.0.beta1,3.1.21)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.2.0,3.2.6)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "rack", "source": "cna", "vendor": "rack"}, "product": "rack", "vendor": "rack"}], "analysis": {"en": {"generated_at": "2026-04-02T23:17:12.820933+00:00", "value": {"mitigation_remediation": ["Upgrade Rack to version 2.2.23, 3.1.21, 3.2.6, or any later release"], "summary": {"action": "Apply patch", "impact": "Incorrect Content\u2011Length set in HTTP responses can cause framing errors and response desynchronization"}, "threat_synthesis": {"affected_systems": "The affected product is Rack, a Ruby web server framework. Any release earlier than 2.2.23, 3.1.21, or 3.2.6 is vulnerable; the issue is identified by the rack:rack CPE.", "description_and_impact": "Rack is a modular Ruby web server interface. In versions prior to 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail incorrectly calculates the Content\u2011Length header by using String#size instead of String#bytesize when the response body contains multibyte UTF\u20118 characters. If an attacker requests a non\u2011existent path that includes percent\u2011encoded UTF\u20118 characters, the resulting 404 response reflects the requested path and the faulty Content\u2011Length is used. The declared length is smaller than the actual number of bytes transmitted, which leads to incorrect HTTP framing and may create response desynchronization for downstream consumers that rely on the Content\u2011Length value.", "risk_and_exploitability": "The CVSS score of 4.8 indicates a moderate impact. No EPSS score is available and the vulnerability is not listed in the CISA KEV catalog. The likely attack vector is a remote HTTP request that targets the application; no local privilege escalation is required. Because exploitation only requires forging a URL with percent\u2011encoded UTF\u20118 characters, the threat is limited to intentional response framing issues rather than data compromise or privilege gain."}}}}, "created": "2026-04-03T07:36:07.426587+00:00", "updated": "2026-04-03T09:18:29.679711+00:00", "vendors": ["rack", "rack$PRODUCT$rack"]}