{"id":"CVE-2026-92707","title":"MessagePack for C# is a MessagePack serializer for C#","summary":"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 …","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwe":["CWE-1325"],"vendor":"MessagePack","product":"MessagePack","affected":["MessagePack < 2.5.303","MessagePack >= 3.0.0, < 3.1.9"],"patched":["MessagePack 2.5.303","MessagePack 3.1.9"],"published":"2026-10-15","updated":"2026-10-15","sourceUpdated":"2026-10-15T19:17:48.703","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-92707","references":[{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a","label":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c","label":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303","label":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9","label":"security-advisories@github.com"},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h","label":"security-advisories@github.com"},{"url":"https://github.com/advisories/GHSA-qhrr-8q5h-9q3h"}],"tags":["nvd","ghsa","nuget","cve.org"],"aliases":["GHSA-qhrr-8q5h-9q3h"],"ecosystem":"nuget","ingestedAt":"2026-10-15T19:25:46.438Z","ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-15T20:10:28.719217Z"},"slug":"CVE-2026-92707","body":"## Overview\n\nMessagePack 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-92707)\n\nAffected packages:\n\n- `MessagePack < 2.5.303`\n- `MessagePack >= 3.0.0, < 3.1.9`\n\nPatched in:\n\n- `MessagePack 2.5.303`\n- `MessagePack 3.1.9`\n\nSource: https://github.com/advisories/GHSA-qhrr-8q5h-9q3h","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}