diff --git a/ext/gd/gd.c b/ext/gd/gd.c
index 336ddef9c6b..2e7ba79faf7 100644
--- a/ext/gd/gd.c
+++ b/ext/gd/gd.c
@@ -686,6 +686,12 @@ PHP_FUNCTION(imageloadfont)
 		font->w = FLIPWORD(font->w);
 		font->h = FLIPWORD(font->h);
 		font->nchars = FLIPWORD(font->nchars);
+		if (overflow2(font->nchars, font->h) || overflow2(font->nchars * font->h, font->w )) {
+			php_error_docref(NULL, E_WARNING, "Error reading font, invalid font header");
+			efree(font);
+			php_stream_close(stream);
+			RETURN_FALSE;
+		}
 		body_size = font->w * font->h * font->nchars;
 	}
 
@@ -696,6 +702,7 @@ PHP_FUNCTION(imageloadfont)
 		RETURN_FALSE;
 	}
 
+	ZEND_ASSERT(body_size > 0);
 	font->data = emalloc(body_size);
 	b = 0;
 	while (b < body_size && (n = php_stream_read(stream, &font->data[b], body_size - b)) > 0) {
diff --git a/ext/gd/tests/bug81739.phpt b/ext/gd/tests/bug81739.phpt
new file mode 100644
index 00000000000..cc2a90381ba
--- /dev/null
+++ b/ext/gd/tests/bug81739.phpt
@@ -0,0 +1,24 @@
+--TEST--
+Bug #81739 (OOB read due to insufficient validation in imageloadfont())
+--SKIPIF--
+<?php
+if (!extension_loaded("gd")) die("skip gd extension not available");
+?>
+--FILE--
+<?php
+$s = fopen(__DIR__ . "/font.font", "w");
+// header without character data
+fwrite($s, "\x01\x00\x00\x00\x20\x00\x00\x00\x08\x00\x00\x00\x08\x00\x00\x00");
+fclose($s);
+var_dump(imageloadfont(__DIR__ . "/font.font"));
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__ . "/font.font");
+?>
+--EXPECTF--
+Warning: imageloadfont(): %croduct of memory allocation multiplication would exceed INT_MAX, failing operation gracefully
+ in %s on line %d
+
+Warning: imageloadfont(): Error reading font, invalid font header in %s on line %d
+bool(false)
\ No newline at end of file