openldap: avoid indexing the result at -1 for blank responses

Reported-by: Joshua Rogers
Closes #18600

diff --git a/lib/openldap.c b/lib/openldap.c
index da26d4a78d0638af65053b54d32e3b8ed32895c2..1f8737f5243ab0e44e043dedb80a79602ffbf953 100644 (file)
--- a/lib/openldap.c
+++ b/lib/openldap.c
@@ -1172,7 +1172,8 @@ static CURLcode oldap_recv(struct Curl_easy *data, int sockindex, char *buf,
         if(!binary) {
           /* check for leading or trailing whitespace */
           if(ISBLANK(bvals[i].bv_val[0]) ||
-             ISBLANK(bvals[i].bv_val[bvals[i].bv_len - 1]))
+             (bvals[i].bv_len &&
+              ISBLANK(bvals[i].bv_val[bvals[i].bv_len - 1])))
             binval = TRUE;
           else {
             /* check for unprintable characters */