diff --git a/mcp/agent/requirements.txt b/mcp/agent/requirements.txt
index 64c7c5b969..0cb44cf5b6 100644
--- a/mcp/agent/requirements.txt
+++ b/mcp/agent/requirements.txt
@@ -134,9 +134,9 @@ attrs==25.3.0 \
     #   aiohttp
     #   jsonschema
     #   referencing
-authlib==1.6.3 \
-    --hash=sha256:7ea0f082edd95a03b7b72edac65ec7f8f68d703017d7e37573aee4fc603f2a48 \
-    --hash=sha256:9f7a982cc395de719e4c2215c5707e7ea690ecf84f1ab126f28c053f4219e610
+authlib==1.6.6 \
+    --hash=sha256:45770e8e056d0f283451d9996fbb59b70d45722b45d854d58f32878d0a40c38e \
+    --hash=sha256:7d9e9bc535c13974313a87f53e8430eb6ea3d1cf6ae4f6efcd793f2e949143fd
     # via google-adk
 cachetools==5.5.2 \
     --hash=sha256:1a661caa9175d26759571b2e19580f9d6393969e5dfca11fdb1f947a23e640d4 \