{"id":"CVE-2026-92707","sourceIdentifier":"security-advisories@github.com","published":"2026-10-15T19:17:48.703","lastModified":"2026-10-16T16:00:33.533","vulnStatus":"Awaiting Analysis","cveTags":[],"descriptions":[{"lang":"en","value":"MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.303 and 3.1.9, deserializing attacker-controlled MessagePack data as System.Object through PrimitiveObjectFormatter can cause excessive memory allocation. The formatter allocates an object[] from each declared array length before the configured object-graph depth limit rejects the input, while nested array headers can reuse the same trailing unread bytes to satisfy per-header length validation. A comparatively small payload can therefore keep many large arrays alive at once. When an attacker can submit such data repeatedly, the allocations can cause severe managed-heap pressure, excessive garbage collection, process termination, or loss of service. Exposure requires an application to deserialize untrusted data through the affected formatter path and permit repeated attacker-controlled submissions, such as a reachable ASP.NET Core SignalR hub method with an object parameter and AddMessagePackProtocol() enabled. This issue is fixed in versions 2.5.303 and 3.1.9."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"MessagePack-CSharp","product":"MessagePack-CSharp","versions":[{"version":"< 2.5.303","status":"affected"},{"version":">= 3.0.0, < 3.1.9","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","baseScore":5.3,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW"},"exploitabilityScore":3.9,"impactScore":1.4}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-15T20:10:28.719217Z","id":"CVE-2026-92707","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-1325"}]}],"references":[{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a","source":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c","source":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303","source":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9","source":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h","source":"security-advisories@github.com"}]}