https://github.com/apache/httpd/pull/578

Index: modules/md/md_ocsp.c
--- modules/md/md_ocsp.c.orig
+++ modules/md/md_ocsp.c
@@ -531,7 +531,7 @@ static const char *certid_summary(const OCSP_CERTID *c
         bn = ASN1_INTEGER_to_BN(aserial, NULL);
         s = BN_bn2hex(bn);
         serial = apr_pstrdup(p, s);
-        OPENSSL_free((void*)bn);
+        BN_free(bn);
         OPENSSL_free((void*)s);
     }
     return apr_psprintf(p, "certid[der=%s, issuer=%s, key=%s, serial=%s]",
