diff --git a/CHANGELOG.md b/CHANGELOG.md
index 508ed0ce5c..6b81caf51f 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.
+- _Upcoming breaking change_: Add a deprecation warning for customers using CodeQL version 2.21.2 and earlier. These versions of CodeQL were discontinued on 24 September 2026 alongside GitHub Enterprise Server 3.17, and will be unsupported by the next minor release of the CodeQL Action. [#4188](https://github.com/github/codeql-action/pull/4188)
 
 ## 4.38.2 - 24 Sept 2026
 
diff --git a/README.md b/README.md
index 530c028f97..8c4fc46631 100644
--- a/README.md
+++ b/README.md
@@ -72,12 +72,11 @@ We typically release new minor versions of the CodeQL Action and Bundle when a n
 
 | Minimum CodeQL Action | Minimum CodeQL Bundle Version | GitHub Environment | Notes |
 |-----------------------|-------------------------------|--------------------|-------|
+| `v4.36.2` | `2.25.6` | Enterprise Server 3.22 | |
 | `v4.33.0` | `2.24.3` | Enterprise Server 3.21 | |
 | `v4.31.10` | `2.23.9` | Enterprise Server 3.20 | |
 | `v3.29.11` | `2.22.4` | Enterprise Server 3.19 | |
 | `v3.28.21` | `2.21.3` | Enterprise Server 3.18 | |
-| `v3.28.12` | `2.20.7` | Enterprise Server 3.17 | |
-| `v3.28.6` | `2.20.3` | Enterprise Server 3.16 | |
 
 See the full list of GHES release and deprecation dates at [GitHub Enterprise Server releases](https://docs.github.com/en/enterprise-server/admin/all-releases#releases-of-github-enterprise-server).
 
diff --git a/lib/entry-points.js b/lib/entry-points.js
index 091132b1c8..566c3d087f 100644
--- a/lib/entry-points.js
+++ b/lib/entry-points.js
@@ -145362,7 +145362,7 @@ var semver = __toESM(require_semver2());
 
 // src/api-compatibility.json
 var maximumVersion = "3.23";
-var minimumVersion = "3.17";
+var minimumVersion = "3.18";
 
 // src/json/index.ts
 function parseString(data) {
@@ -152875,9 +152875,9 @@ async function getCombinedTracerConfig(logger, codeql, config) {
 // src/codeql.ts
 var cachedCodeQL = void 0;
 var CODEQL_MINIMUM_VERSION = "2.19.4";
-var CODEQL_NEXT_MINIMUM_VERSION = "2.20.7";
-var GHES_VERSION_MOST_RECENTLY_DEPRECATED = "3.16";
-var GHES_MOST_RECENT_DEPRECATION_DATE = "2026-07-01";
+var CODEQL_NEXT_MINIMUM_VERSION = "2.21.3";
+var GHES_VERSION_MOST_RECENTLY_DEPRECATED = "3.17";
+var GHES_MOST_RECENT_DEPRECATION_DATE = "2026-09-24";
 var EXTRACTION_DEBUG_MODE_VERBOSITY = "progress++";
 function isDiskConfigurationError(e) {
   if (!(e instanceof Error)) {
diff --git a/src/api-compatibility.json b/src/api-compatibility.json
index aa7840e384..c1122fb2a9 100644
--- a/src/api-compatibility.json
+++ b/src/api-compatibility.json
@@ -1 +1 @@
-{"maximumVersion":"3.23","minimumVersion":"3.17"}
+{"maximumVersion":"3.23","minimumVersion":"3.18"}
diff --git a/src/codeql.ts b/src/codeql.ts
index a4da8ad68a..90c8d73af5 100644
--- a/src/codeql.ts
+++ b/src/codeql.ts
@@ -258,17 +258,17 @@ const CODEQL_MINIMUM_VERSION = "2.19.4";
 /**
  * This version will shortly become the oldest version of CodeQL that the Action will run with.
  */
-const CODEQL_NEXT_MINIMUM_VERSION = "2.20.7";
+const CODEQL_NEXT_MINIMUM_VERSION = "2.21.3";
 
 /**
  * This is the version of GHES that was most recently deprecated.
  */
-const GHES_VERSION_MOST_RECENTLY_DEPRECATED = "3.16";
+const GHES_VERSION_MOST_RECENTLY_DEPRECATED = "3.17";
 
 /**
  * This is the deprecation date for the version of GHES that was most recently deprecated.
  */
-const GHES_MOST_RECENT_DEPRECATION_DATE = "2026-07-01";
+const GHES_MOST_RECENT_DEPRECATION_DATE = "2026-09-24";
 
 /** The CLI verbosity level to use for extraction in debug mode. */
 const EXTRACTION_DEBUG_MODE_VERBOSITY = "progress++";