SNMPv3 HMAC verification in (1) Net-SNMP 5.2.x before 5.2.4.1, 5.3.x before 5.3.2.1, and 5.4.x before 5.4.1.1; (2) UCD-SNMP; (3) eCos; (4) Juniper Session and Resource Control (SRC) C-series 1.0.0 through 2.0.0; (5) NetApp (aka Network Appliance) Data ONTAP 7.3RC1 and 7.3RC2; (6) SNMP Research before 16.2; (7) multiple Cisco IOS, CatOS, ACE, and Nexus products; (8) Ingate Firewall 3.1.0 and later and SIParator 3.1.0 and later; (9) HP OpenView SNMP Emanate Master Agent 15.x; and possibly other products relies on the client to specify the HMAC length, which makes it easier for remote attackers to bypass SNMP authentication via a length value of 1, which only checks the first byte.