{"id":"CVE-2026-92707","summary":"MessagePack: Nested arrays can blow past buffer length limits","details":"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.","aliases":["GHSA-qhrr-8q5h-9q3h"],"modified":"2026-10-16T10:46:30.899550753Z","published":"2026-10-15T18:35:49.074Z","database_specific":{"cwe_ids":["CWE-1325"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92707.json","cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92707.json"},{"type":"FIX","url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a"},{"type":"FIX","url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c"},{"type":"WEB","url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303"},{"type":"WEB","url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9"},{"type":"ADVISORY","url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-92707"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/messagepack-csharp/messagepack-csharp","events":[{"introduced":"0"},{"fixed":"7fd78bbf3476e03beae8b0f7a521125525a8a64a"},{"fixed":"aa16e71ae548645050f0a6798874540f3149681b"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"2.5.303"},{"introduced":"3.0.0"},{"fixed":"3.1.9"}],"source":"AFFECTED_FIELD"}}],"versions":["v2.5.302","v3.1.8","v3.1.7","v2.5.205","v3.1.6","v3.1.5","v2.5.198","v3.1.4","v3.1.3","v3.1.2","v3.1.1","v3.1.0","v3.0.301","v3.0.300","v3.0.3","v2.5.192","v2.5.187","v2.5.172","v2.5.171","v2.5.168","v2.5.140","v2.5.129","v2.5.108","v2.5.124","v2.5.103","v2.4.59","v2.5.94","v2.4.35","v2.4.23-alpha","v2.3.85","v2.1.115","v2.3.75","v2.2.113","v2.2.85","v2.2.60","v2.1.194","v2.1.165","v2.1.152","v2.1.143","v2.1.90","v2.1.80","v2.0.270-rc","v2.0.204-beta","v2.0.123-beta","v2.0.119-beta","v2.0.110-alpha","v2.0.94-alpha","v1.7.3.4","v1.7.3.3","v1.7.3.2","v1.7.3.1","v1.7.3","v1.7.2","v1.7.0","v1.6.2","v1.6.1.2","v1.6.1","v1.6.0","v1.5.1","v1.5.0","v1.4.4","v1.4.2","v1.4.1","v1.4.0","v1.3.3","v1.3.2","v1.3.1","v1.3.0","v1.2.3","v1.2.1","v1.2.0","v1.1.2","v1.1.1","v1.0.3","v1.0.2","1.0.1","0.2.0-beta","0.1.0-beta"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-92707.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}