diff --git a/NEWS b/NEWS
index e027d6c139ee..cf2e1ab2e536 100644
--- a/NEWS
+++ b/NEWS
@@ -123,6 +123,8 @@ PHP                                                                        NEWS
     in a php://filter URL. (Sjoerd Langkemper)
   . Improved performance of array_chunk() when not preserving keys.
     (mehmetcansahin)
+  . Fixed bug GH-21292 (proc_close() returns raw signal number,
+    indistinguishable from normal exit code). (Alies Lapatsin)
 
 - URI:
   . Fix casing of enum cases in UriHostType and UrlHostType to match the RFC
diff --git a/UPGRADING b/UPGRADING
index 46cf4cafab12..9f35859138dc 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -31,6 +31,16 @@ PHP 8.7 UPGRADE NOTES
   . The number of filters that can be chained in a php://filter URL is limited
     to 16 by default. Set the stream context option max_filter_count to change
     this.
+  . On Unix systems, proc_close() now reports termination by a signal as
+    128 + the signal number, following the shell convention, instead of the
+    raw wait status (e.g. 137 instead of 9 for SIGKILL). This also applies when
+    proc_get_status() observed the termination first; previously proc_close()
+    returned -1 in that case. Normal exit codes are unchanged.
+  . On Unix systems, proc_get_status() now also caches the status of a child
+    terminated by a signal, as it does for normal exits since PHP 8.3.
+    Repeated calls keep reporting "signaled" => true and the "termsig" value,
+    and "cached" is true. Previously, calls after the first one reported
+    "signaled" => false and "termsig" => 0.
 
 ========================================
 2. New Features
diff --git a/ext/standard/proc_open.c b/ext/standard/proc_open.c
index 4fd24058f7cb..9ecc57bcbac4 100644
--- a/ext/standard/proc_open.c
+++ b/ext/standard/proc_open.c
@@ -256,10 +256,10 @@ static pid_t waitpid_cached(php_process_handle *proc, int *wait_status, int opti
 
 	pid_t wait_pid = waitpid(proc->child, wait_status, options);
 
-	/* The "exit" status is the final status of the process.
+	/* The "exit" and "terminated by signal" statuses are final statuses of the process.
 	 * If we were to cache the status unconditionally,
 	 * we would return stale statuses in the future after the process continues. */
-	if (wait_pid > 0 && WIFEXITED(*wait_status)) {
+	if (wait_pid > 0 && (WIFEXITED(*wait_status) || WIFSIGNALED(*wait_status))) {
 		proc->has_cached_exit_wait_status = true;
 		proc->cached_exit_wait_status_value = *wait_status;
 	}
@@ -317,11 +317,13 @@ static void proc_open_rsrc_dtor(zend_resource *rsrc)
 
 	if (wait_pid <= 0) {
 		FG(pclose_ret) = -1;
+	} else if (WIFEXITED(wstatus)) {
+		FG(pclose_ret) = WEXITSTATUS(wstatus);
+	} else if (WIFSIGNALED(wstatus)) {
+		/* Follow the bash/shell convention: 128 + signal number */
+		FG(pclose_ret) = 128 + WTERMSIG(wstatus);
 	} else {
-		if (WIFEXITED(wstatus)) {
-			wstatus = WEXITSTATUS(wstatus);
-		}
-		FG(pclose_ret) = wstatus;
+		FG(pclose_ret) = -1;
 	}
 
 #else
diff --git a/ext/standard/tests/general_functions/bug39322.phpt b/ext/standard/tests/general_functions/bug39322.phpt
index 162f2babdaac..cfa56de1264a 100644
--- a/ext/standard/tests/general_functions/bug39322.phpt
+++ b/ext/standard/tests/general_functions/bug39322.phpt
@@ -30,7 +30,7 @@ array(9) {
   ["pid"]=>
   int(%d)
   ["cached"]=>
-  bool(false)
+  bool(true)
   ["running"]=>
   bool(false)
   ["signaled"]=>
diff --git a/ext/standard/tests/general_functions/gh21292.phpt b/ext/standard/tests/general_functions/gh21292.phpt
new file mode 100644
index 000000000000..43c3dd00c7aa
--- /dev/null
+++ b/ext/standard/tests/general_functions/gh21292.phpt
@@ -0,0 +1,56 @@
+--TEST--
+GH-21292 (proc_close() returns raw signal number, indistinguishable from normal exit code)
+--SKIPIF--
+<?php
+if (PHP_OS_FAMILY === 'Windows') die('skip Not for Windows');
+if (!is_executable('/bin/sh')) die('skip /bin/sh not available');
+?>
+--FILE--
+<?php
+
+function spawn(string $script) {
+    $process = proc_open(
+        ['/bin/sh', '-c', $script],
+        [['pipe', 'r'], ['pipe', 'w'], ['pipe', 'w']],
+        $pipes
+    );
+    foreach ($pipes as $pipe) {
+        fclose($pipe);
+    }
+    return $process;
+}
+
+echo "Killed by SIGKILL:\n";
+var_dump(proc_close(spawn('kill -9 $$')));
+
+echo "Normal exit:\n";
+var_dump(proc_close(spawn('exit 42')));
+var_dump(proc_close(spawn('exit 9')));
+var_dump(proc_close(spawn('exit 137')));
+
+echo "Killed by SIGKILL, status polled before proc_close():\n";
+$process = spawn('kill -9 $$');
+for ($i = 0; $i < 500 && proc_get_status($process)['running']; $i++) {
+    usleep(10000);
+}
+$status = proc_get_status($process);
+var_dump($status['signaled'], $status['termsig']);
+$status = proc_get_status($process);
+var_dump($status['cached'], $status['signaled'], $status['termsig']);
+var_dump(proc_close($process));
+
+?>
+--EXPECT--
+Killed by SIGKILL:
+int(137)
+Normal exit:
+int(42)
+int(9)
+int(137)
+Killed by SIGKILL, status polled before proc_close():
+bool(true)
+int(9)
+bool(true)
+bool(true)
+int(9)
+int(137)
diff --git a/ext/standard/tests/general_functions/proc_open02.phpt b/ext/standard/tests/general_functions/proc_open02.phpt
index dd2e6902a411..864d1001930a 100644
--- a/ext/standard/tests/general_functions/proc_open02.phpt
+++ b/ext/standard/tests/general_functions/proc_open02.phpt
@@ -59,7 +59,7 @@ array(9) {
   ["pid"]=>
   int(%d)
   ["cached"]=>
-  bool(false)
+  bool(true)
   ["running"]=>
   bool(false)
   ["signaled"]=>