diff --git a/CHANGELOG.md b/CHANGELOG.md
index 508ed0ce5c..d81e4ede34 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_: CodeQL version 2.21.2 and earlier 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. Added a deprecation warning for customers using these versions of CodeQL. [#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++";