diff --git a/ext/dom/document.c b/ext/dom/document.c
index 759086569afb..31b889125269 100644
--- a/ext/dom/document.c
+++ b/ext/dom/document.c
@@ -1157,6 +1157,9 @@ char *_dom_get_valid_file_path(char *source, char *resolved_path, int resolved_p
 	int isFileUri = 0;
 
 	uri = xmlCreateURI();
+	if (uri == NULL) {
+		return NULL;
+	}
 	escsource = xmlURIEscapeStr((xmlChar *) source, (xmlChar *) ":");
 	xmlParseURIReference(uri, (char *) escsource);
 	xmlFree(escsource);
diff --git a/ext/openssl/openssl.c b/ext/openssl/openssl.c
index 0b0fa3b7d84a..8182fb3df382 100644
--- a/ext/openssl/openssl.c
+++ b/ext/openssl/openssl.c
@@ -7345,6 +7345,12 @@ PHP_FUNCTION(openssl_digest)
 	sigbuf = zend_string_alloc(siglen, 0);
 
 	md_ctx = EVP_MD_CTX_create();
+
+	// add check against NULL
+	if (md_ctx == NULL) {
+		RETURN_FALSE;
+	}
+
 	if (EVP_DigestInit(md_ctx, mdtype) &&
 			EVP_DigestUpdate(md_ctx, (unsigned char *)data, data_len) &&
 			EVP_DigestFinal (md_ctx, (unsigned char *)ZSTR_VAL(sigbuf), &siglen)) {
diff --git a/ext/xmlreader/php_xmlreader.c b/ext/xmlreader/php_xmlreader.c
index 137c12f7151a..4ec3cae16efb 100644
--- a/ext/xmlreader/php_xmlreader.c
+++ b/ext/xmlreader/php_xmlreader.c
@@ -212,6 +212,9 @@ char *_xmlreader_get_valid_file_path(char *source, char *resolved_path, int reso
 	int isFileUri = 0;
 
 	uri = xmlCreateURI();
+	if (uri == NULL) {
+		return NULL;
+	}
 	escsource = xmlURIEscapeStr((xmlChar *)source, (xmlChar *)":");
 	xmlParseURIReference(uri, (const char *)escsource);
 	xmlFree(escsource);
diff --git a/ext/xmlwriter/php_xmlwriter.c b/ext/xmlwriter/php_xmlwriter.c
index 8fd5f1223d43..abb135780887 100644
--- a/ext/xmlwriter/php_xmlwriter.c
+++ b/ext/xmlwriter/php_xmlwriter.c
@@ -109,6 +109,9 @@ static char *_xmlwriter_get_valid_file_path(char *source, char *resolved_path, i
 	int isFileUri = 0;
 
 	uri = xmlCreateURI();
+	if (uri == NULL) {
+		return NULL;
+	}
 	escsource = xmlURIEscapeStr((xmlChar *)source, (xmlChar *) ":");
 	xmlParseURIReference(uri, (char *)escsource);
 	xmlFree(escsource);