diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c9c05594a..12904ac941 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,7 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 
 ## [UNRELEASED]
 
-No user facing changes.
+- Update default CodeQL bundle version to 2.21.0. [#2838](https://github.com/github/codeql-action/pull/2838)
 
 ## 3.28.13 - 24 Mar 2025
 
diff --git a/lib/defaults.json b/lib/defaults.json
index 6473524ce6..9d23944a75 100644
--- a/lib/defaults.json
+++ b/lib/defaults.json
@@ -1,6 +1,6 @@
 {
-    "bundleVersion": "codeql-bundle-v2.20.7",
-    "cliVersion": "2.20.7",
-    "priorBundleVersion": "codeql-bundle-v2.20.6",
-    "priorCliVersion": "2.20.6"
+    "bundleVersion": "codeql-bundle-v2.21.0",
+    "cliVersion": "2.21.0",
+    "priorBundleVersion": "codeql-bundle-v2.20.7",
+    "priorCliVersion": "2.20.7"
 }
diff --git a/src/defaults.json b/src/defaults.json
index 13392d33ae..eb2699fae7 100644
--- a/src/defaults.json
+++ b/src/defaults.json
@@ -1,6 +1,6 @@
 {
-  "bundleVersion": "codeql-bundle-v2.20.7",
-  "cliVersion": "2.20.7",
-  "priorBundleVersion": "codeql-bundle-v2.20.6",
-  "priorCliVersion": "2.20.6"
+  "bundleVersion": "codeql-bundle-v2.21.0",
+  "cliVersion": "2.21.0",
+  "priorBundleVersion": "codeql-bundle-v2.20.7",
+  "priorCliVersion": "2.20.7"
 }