diff --git a/NEWS b/NEWS
index ec32bdfd088..16b10267098 100644
--- a/NEWS
+++ b/NEWS
@@ -27,7 +27,11 @@ PHP                                                                        NEWS
 - PDO_Firebird:
   . Fixed GH-15604 (Always make input parameters nullable). (sim1984)
 
-27 Aug 2024, PHP 8.4.0beta4
+- Streams:
+  . Fixed bug GH-15628 (php_stream_memory_get_buffer() not zero-terminated).
+    (cmb)
+
+29 Aug 2024, PHP 8.4.0beta4
 
 - Core:
   . Fixed bug GH-15408 (MSan false-positve on zend_max_execution_timer).
diff --git a/main/streams/memory.c b/main/streams/memory.c
index 62d36906635..ce11aec382b 100644
--- a/main/streams/memory.c
+++ b/main/streams/memory.c
@@ -66,6 +66,7 @@ static ssize_t php_stream_memory_write(php_stream *stream, const char *buf, size
 	if (count) {
 		ZEND_ASSERT(buf != NULL);
 		memcpy(ZSTR_VAL(ms->data) + ms->fpos, (char*) buf, count);
+		ZSTR_VAL(ms->data)[ZSTR_LEN(ms->data)] = '\0';
 		ms->fpos += count;
 	}
 	return count;
@@ -241,6 +242,7 @@ static int php_stream_memory_set_option(php_stream *stream, int option, int valu
 						size_t old_size = ZSTR_LEN(ms->data);
 						ms->data = zend_string_realloc(ms->data, newsize, 0);
 						memset(ZSTR_VAL(ms->data) + old_size, 0, newsize - old_size);
+						ZSTR_VAL(ms->data)[ZSTR_LEN(ms->data)] = '\0';
 					}
 					return PHP_STREAM_OPTION_RETURN_OK;
 			}