diff --git a/Directory.Packages.props b/Directory.Packages.props
index d23bfb1..3c6e39b 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -19,7 +19,7 @@
     <!-- Direct pins: lift StreamJsonRpc 2.24.92's vulnerable transitive
          floors (MessagePack 2.5.198 — GHSA-hv8m-jj95-wg3x high + 8
          moderates; Nerdbank.MessagePack 1.1.62 — 2 moderates). -->
-    <PackageVersion Include="MessagePack" Version="2.5.302" />
+    <PackageVersion Include="MessagePack" Version="3.1.8" />
     <PackageVersion Include="Nerdbank.MessagePack" Version="1.2.36" />
   </ItemGroup>
   <!-- Roslyn (C# provider) -->