diff --git a/libcli/security/dom_sid.c b/libcli/security/dom_sid.c
index 0c88900..350a14f 100644
--- a/libcli/security/dom_sid.c
+++ b/libcli/security/dom_sid.c
@@ -117,6 +117,10 @@ bool dom_sid_parse(const char *sidstr, struct dom_sid *ret)
 		if (sidstr[i] == '-') num_sub_auths++;
 	}
 
+	if (num_sub_auths > MAXSUBAUTHS) {
+		return false;
+	}
+
 	ret->sid_rev_num = rev;
 	ret->id_auth[0] = 0;
 	ret->id_auth[1] = 0;
diff --git a/libcli/security/dom_sid.h b/libcli/security/dom_sid.h
index e892535..748e009 100644
--- a/libcli/security/dom_sid.h
+++ b/libcli/security/dom_sid.h
@@ -40,5 +40,9 @@ bool dom_sid_in_domain(const struct dom_sid *domain_sid,
 		       const struct dom_sid *sid);
 char *dom_sid_string(TALLOC_CTX *mem_ctx, const struct dom_sid *sid);
 
+#ifndef MAXSUBAUTHS
+#define MAXSUBAUTHS 15 /* max sub authorities in a SID */
+#endif
+
 #endif /*_DOM_SID_H_*/
 
diff --git a/source3/lib/util_sid.c b/source3/lib/util_sid.c
index 97284af..52e8448 100644
--- a/source3/lib/util_sid.c
+++ b/source3/lib/util_sid.c
@@ -408,6 +408,9 @@ bool sid_parse(const char *inbuf, size_t len, DOM_SID *sid)
 
 	sid->sid_rev_num = CVAL(inbuf, 0);
 	sid->num_auths = CVAL(inbuf, 1);
+	if (sid->num_auths > MAXSUBAUTHS) {
+		return false;
+	}
 	memcpy(sid->id_auth, inbuf+2, 6);
 	if (len < 8 + sid->num_auths*4)
 		return False;
diff --git a/source3/libads/ldap.c b/source3/libads/ldap.c
index 1fb541d..08b8311 100644
--- a/source3/libads/ldap.c
+++ b/source3/libads/ldap.c
@@ -2128,7 +2128,9 @@ static void dump_sid(ADS_STRUCT *ads, const char *field, struct berval **values)
 	for (i=0; values[i]; i++) {
 		DOM_SID sid;
 		fstring tmp;
-		sid_parse(values[i]->bv_val, values[i]->bv_len, &sid);
+		if (!sid_parse(values[i]->bv_val, values[i]->bv_len, &sid)) {
+			continue;
+		}
 		printf("%s: %s\n", field, sid_to_fstring(tmp, &sid));
 	}
 }
diff --git a/source3/libsmb/cliquota.c b/source3/libsmb/cliquota.c
index e40dac3..2af5b22 100644
--- a/source3/libsmb/cliquota.c
+++ b/source3/libsmb/cliquota.c
@@ -117,7 +117,9 @@ static bool parse_user_quota_record(const char *rdata, unsigned int rdata_count,
 	}
 #endif /* LARGE_SMB_OFF_T */
 
-	sid_parse(rdata+40,sid_len,&qt.sid);
+	if (!sid_parse(rdata+40,sid_len,&qt.sid)) {
+		return false;
+	}
 
 	qt.qtype = SMB_USER_QUOTA_TYPE;
 
diff --git a/source3/smbd/nttrans.c b/source3/smbd/nttrans.c
index 4bfbcd1..2834f08 100644
--- a/source3/smbd/nttrans.c
+++ b/source3/smbd/nttrans.c
@@ -2080,7 +2080,11 @@ static void call_nt_transact_ioctl(connection_struct *conn,
 		/* unknown 4 bytes: this is not the length of the sid :-(  */
 		/*unknown = IVAL(pdata,0);*/
 
-		sid_parse(pdata+4,sid_len,&sid);
+		if (!sid_parse(pdata+4,sid_len,&sid)) {
+			reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+			return;
+		}
+
 		DEBUGADD(10, ("for SID: %s\n", sid_string_dbg(&sid)));
 
 		if (!sid_to_uid(&sid, &uid)) {
@@ -2336,7 +2340,10 @@ static void call_nt_transact_get_user_quota(connection_struct *conn,
 				break;
 			}
 
-			sid_parse(pdata+8,sid_len,&sid);
+			if (!sid_parse(pdata+8,sid_len,&sid)) {
+				reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+				return;
+			}
 
 			if (vfs_get_ntquota(fsp, SMB_USER_QUOTA_TYPE, &sid, &qt)!=0) {
 				ZERO_STRUCT(qt);
@@ -2517,7 +2524,11 @@ static void call_nt_transact_set_user_quota(connection_struct *conn,
 	}
 #endif /* LARGE_SMB_OFF_T */
 
-	sid_parse(pdata+40,sid_len,&sid);
+	if (!sid_parse(pdata+40,sid_len,&sid)) {
+		reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+		return;
+	}
+
 	DEBUGADD(8,("SID: %s\n", sid_string_dbg(&sid)));
 
 	/* 44 unknown bytes left... */