Publish GHSA-92vj-hp7m-gwcj

Author: advisory-database[bot]

advisories/github-reviewed/2026/05/GHSA-92vj-hp7m-gwcj/GHSA-92vj-hp7m-gwcj.json

@@ -0,0 +1,59 @@
+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-92vj-hp7m-gwcj",
+  "modified": "2026-05-29T20:02:59Z",
+  "published": "2026-05-29T20:02:59Z",
+  "aliases": [],
+  "summary": "Nerdbank.MessagePack has Inefficient CPU Computation",
+  "details": "### Impact\n\nApplications that call `OptionalConverters.WithExpandoObjectConverter` and deserialize untrusted data are open to a vulnerability by which an attacker can exploit a `O(n²)` algorithm to burn an inordinate amount of CPU effort by adding a great many properties to an `ExpandoObject`, whose `Add` method is implemented as an `O(n)` algorithm.\n\n### Patches\n\nUpdate to a patched version.\n\nIf a project's `ExpandoObject` data requires more than 128 properties, the default limit should be changed:\n\n```cs\nthis.Serializer = this.Serializer with\n{\n\tStartingContext = this.Serializer.StartingContext with\n\t{\n\t\tSecurity = this.Serializer.StartingContext.Security with\n\t\t{\n\t\t\tExpandoObjectMaxPropertyCount = 256, // Set this to whatever limit is required by your application\n\t\t},\n\t},\n};\n```\n\n### Workarounds\n\nAvoid the non-default `WithExpandoObjectConverter` extension method when deserializing untrusted data.\nIf deserializing untrusted data into an `ExpandoObject` is required, developers should write a custom converter for their project that limits the number of properties allowed before initializing the object.",
+  "severity": [
+    {
+      "type": "CVSS_V3",
+      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "NuGet",
+        "name": "Nerdbank.MessagePack"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "fixed": "1.2.4"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/AArnott/Nerdbank.MessagePack/security/advisories/GHSA-92vj-hp7m-gwcj"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/AArnott/Nerdbank.MessagePack/commit/c5a239e4f20c38548de44c4dd2a782efd5e2547c"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/AArnott/Nerdbank.MessagePack"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-1176"
+    ],
+    "severity": "MODERATE",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-05-29T20:02:59Z",
+    "nvd_published_at": null
+  }
+}