{"schemaVersion":3,"id":"CVE-2026-92707","aliases":["GHSA-qhrr-8q5h-9q3h","CGA-54wc-99qp-2ww5","CGA-jxg4-hm96-pcgp","UBUNTU-CVE-2026-92707"],"status":"published","duplicateOf":null,"title":null,"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.","dates":{"published":"2026-10-15T18:35:49.074Z","modified":"2026-10-15T20:12:15.468Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":5.3,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Nuget","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","exploitability":10,"impact":2.3,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Chainguard","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","exploitability":10,"impact":2.3,"computed":true}]},"epss":{"probability":0.00648,"percentile":0.50143,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-16T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00648,"percentile":0.50143}],"last30":[{"date":"2026-10-16T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00648,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00648,"percentile":0.50143}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-1325","name":"Improperly Controlled Sequential Memory Allocation","description":"The product manages a group of objects or resources and performs a separate memory allocation for each object, but it does not properly limit the total amount of memory that is consumed by all of the combined objects.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/1325.html"}],"affected":[{"vendor":"chainguard","product":"azure-functions-extension-bundles-4","name":"azure-functions-extension-bundles-4","label":"azure-functions-extension-bundles-4","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/azure-functions-extension-bundles-4","purlType":"apk","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 4.40.0-r1","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 4.40.0-r1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"dotnet10","name":"dotnet10","label":"dotnet10","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/dotnet10","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"dotnet11","name":"dotnet11","label":"dotnet11","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/dotnet11","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"dotnet6","name":"dotnet6","label":"dotnet6","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/dotnet6","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"dotnet7","name":"dotnet7","label":"dotnet7","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/dotnet7","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"dotnet8","name":"dotnet8","label":"dotnet8","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/dotnet8","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"messagepack-csharp","product":"messagepack-csharp","name":"MessagePack-CSharp","label":"messagepack-csharp","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 2.5.303","noFixRecorded":false,"fixedIn":null},{"text":"≥ 3.0.0, < 3.1.9","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.5.303 | ≥ 3.0.0, < 3.1.9","eol":null,"hubHref":"/vendor/messagepack-csharp/messagepack-csharp"},{"vendor":"NuGet","product":"MessagePack","name":"MessagePack","label":"MessagePack","ecosystem":"NuGet","cpePart":null,"purl":"pkg:nuget/MessagePack","purlType":"nuget","versions":[{"text":"< 2.5.303","noFixRecorded":false,"fixedIn":null},{"text":"≥ 3.0.0, < 3.1.9","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.5.303 | ≥ 3.0.0, < 3.1.9","eol":null,"hubHref":null}],"affectedCount":8,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h","label":"github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h","hostname":"github.com","tags":["X Refsource CONFIRM","WEB","Advisory"]},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a","label":"github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX"]},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c","label":"github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX"]},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303","label":"github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303","hostname":"github.com","tags":["X Refsource MISC","WEB"]},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9","label":"github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9","hostname":"github.com","tags":["X Refsource MISC","WEB"]},{"url":"https://github.com/MessagePack-CSharp/MessagePack-CSharp","label":"github.com/MessagePack-CSharp/MessagePack-CSharp","hostname":"github.com","tags":["PACKAGE"]},{"url":"https://ubuntu.com/security/CVE-2026-92707","label":"ubuntu.com/security/CVE-2026-92707","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-92707","label":"www.cve.org/CVERecord?id=CVE-2026-92707","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-92707","label":"msrc.microsoft.com/update-guide/vulnerability/CVE-2026-92707","hostname":"msrc.microsoft.com","tags":["REPORT"]},{"url":"https://devblogs.microsoft.com/dotnet/dotnet-and-dotnet-framework-october-2026-servicing-updates","label":"devblogs.microsoft.com/dotnet/dotnet-and-dotnet-framework-october-2026-servicing-updates","hostname":"devblogs.microsoft.com","tags":["REPORT"]},{"url":"https://github.com/dotnet/announcements/issues/473","label":"github.com/dotnet/announcements/issues/473","hostname":"github.com","tags":["REPORT"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92707.json","label":"github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92707.json","hostname":"github.com","tags":["Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-92707","label":"nvd.nist.gov/vuln/detail/CVE-2026-92707","hostname":"nvd.nist.gov","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-15T18:35:49.074Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-10-15T20:12:15.468Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":21,"level":"low","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T03:39:54.274Z","stale":false,"partial":false}}