diff --git a/ruby/ql/lib/change-notes/2023-07-05-rack-env-query-params.md b/ruby/ql/lib/change-notes/2023-07-05-rack-env-query-params.md
new file mode 100644
index 00000000000..807db340146
--- /dev/null
+++ b/ruby/ql/lib/change-notes/2023-07-05-rack-env-query-params.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* The `'QUERY_STRING'` field of a Rack `env` parameter is now recognized as a source of remote user input.
diff --git a/ruby/ql/lib/codeql/ruby/frameworks/rack/internal/App.qll b/ruby/ql/lib/codeql/ruby/frameworks/rack/internal/App.qll
index 4844422ba68..41df3ac0e64 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/rack/internal/App.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/rack/internal/App.qll
@@ -4,6 +4,7 @@
 
 private import codeql.ruby.AST
 private import codeql.ruby.ApiGraphs
+private import codeql.ruby.Concepts
 private import codeql.ruby.DataFlow
 private import codeql.ruby.typetracking.TypeTracker
 private import Response::Private as RP
@@ -77,4 +78,20 @@ module App {
     /** Gets a response returned from this request handler. */
     RP::PotentialResponseNode getAResponse() { result = resp }
   }
+
+  /** A read of the query string via `env['QUERY_STRING']`. */
+  private class EnvQueryStringRead extends Http::Server::RequestInputAccess::Range {
+    EnvQueryStringRead() {
+      this =
+        any(RequestHandler h)
+            .getEnv()
+            .getAnElementRead(ConstantValue::fromStringlikeValue("QUERY_STRING"))
+    }
+
+    override string getSourceType() { result = "Rack env" }
+
+    override Http::Server::RequestInputKind getKind() {
+      result = Http::Server::parameterInputKind()
+    }
+  }
 }
diff --git a/ruby/ql/test/library-tests/frameworks/rack/Rack.expected b/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
index 4cb29e63c2a..8473cf913ca 100644
--- a/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
+++ b/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
@@ -3,11 +3,12 @@ rackRequestHandlers
 | rack.rb:17:3:21:5 | call | rack.rb:17:12:17:18 | the_env | rack.rb:20:5:20:27 | call to [] |
 | rack.rb:30:3:36:5 | call | rack.rb:30:12:30:14 | env | rack.rb:35:5:35:26 | call to [] |
 | rack.rb:40:3:44:5 | call | rack.rb:40:12:40:14 | env | rack.rb:43:5:43:45 | call to [] |
-| rack.rb:60:3:62:5 | call | rack.rb:60:12:60:14 | env | rack.rb:66:7:66:22 | call to [] |
-| rack.rb:60:3:62:5 | call | rack.rb:60:12:60:14 | env | rack.rb:73:5:73:21 | call to [] |
+| rack.rb:60:3:62:5 | call | rack.rb:60:12:60:14 | env | rack.rb:66:7:66:24 | call to [] |
+| rack.rb:60:3:62:5 | call | rack.rb:60:12:60:14 | env | rack.rb:73:5:73:23 | call to [] |
 | rack.rb:79:3:81:5 | call | rack.rb:79:17:79:19 | env | rack.rb:93:5:93:78 | call to finish |
 | rack.rb:98:3:107:5 | call | rack.rb:98:12:98:14 | env | rack.rb:110:5:110:28 | call to [] |
 | rack.rb:98:3:107:5 | call | rack.rb:98:12:98:14 | env | rack.rb:114:5:114:30 | call to [] |
+| rack.rb:119:3:123:5 | call | rack.rb:119:12:119:14 | env | rack.rb:122:5:122:42 | call to [] |
 | rack_apps.rb:6:3:12:5 | call | rack_apps.rb:6:12:6:14 | env | rack_apps.rb:10:12:10:34 | call to [] |
 | rack_apps.rb:16:3:18:5 | call | rack_apps.rb:16:17:16:19 | env | rack_apps.rb:17:5:17:28 | call to [] |
 | rack_apps.rb:21:14:21:50 | -> { ... } | rack_apps.rb:21:17:21:19 | env | rack_apps.rb:21:24:21:48 | call to [] |
@@ -22,3 +23,4 @@ requestInputAccesses
 | rack.rb:100:18:100:28 | call to cookies |
 | rack.rb:103:14:103:23 | call to params |
 | rack.rb:104:18:104:32 | ...[...] |
+| rack.rb:120:14:120:32 | ...[...] |
diff --git a/ruby/ql/test/library-tests/frameworks/rack/rack.rb b/ruby/ql/test/library-tests/frameworks/rack/rack.rb
index 8665cc90162..33d05e87fc0 100644
--- a/ruby/ql/test/library-tests/frameworks/rack/rack.rb
+++ b/ruby/ql/test/library-tests/frameworks/rack/rack.rb
@@ -63,14 +63,14 @@ class Baz
 
   def run(env)
     if env[:foo] == "foo"
-      [200, {}, "foo"]
+      [200, {}, ["foo"]]
     else
       error
     end
   end
 
   def error
-    [400, {}, "nope"]
+    [400, {}, ["nope"]]
   end
 end
 
@@ -114,3 +114,11 @@ class UsesRequest
     [200, {}, "reuse session"]
   end
 end
+
+class UsesEnvQueryParams
+  def call(env)
+    params = env['QUERY_STRING']
+    user = Rack::Utils.parse_query(params)["user"]
+    [200, {}, [lookup_user_profile(user)]]
+  end
+end