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[ CVE-2026-92707 · Published 15 Oct 2026 ]

MessagePack: Nested arrays can blow past buffer length limits

CVSS 5.3 EPSS <1%3 agency advisoriesFix available

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

  • MessagePack 2.5.303Fixed version · GitHub Advisories · nuget package MessagePack: upgrade to 2.5.303 or later (affected < 2.5.303)
  • MessagePack 3.1.9Fixed version · GitHub Advisories · nuget package MessagePack: upgrade to 3.1.9 or later (affected >= 3.0.0, < 3.1.9)

[ Advisories ]Government CERT advisories

  • CERT-FRCERTFR-2026-AVI-1316

    Multiple vulnerabilities in Microsoft products Translated from French

    Multiple vulnerabilities have been discovered in Microsoft products. Some of them allow an attacker to cause remote arbitrary code execution, privilege escalation and remote denial of service.

    CVE-2026-88086CVE-2026-70007CVE-2026-70179+141 more CVEs
  • BSI CERT-BundWID-SEC-2026-3893

    Microsoft Entwicklerwerkzeuge: Multiple vulnerabilities Translated from German

    Risk highCVE-2026-96230CVE-2026-84008CVE-2026-102238+64 more CVEs
  • BSI CERT-BundWID-SEC-2026-3922

    Microsoft Apps: Multiple vulnerabilities Translated from German

    CVE-2026-83844CVE-2026-92707CVE-2026-96188+3 more CVEs

[ Packages ]Affected open-source packages

[ References ]References