A possibility of sensitive host information disclosure was found in the implementation of SNMP protocol as defined in RFC 1065, RFC 1066, and RFC 1067. If the snmpd deamon was running on the host, it served the SNMP queries regardless of the fact, the IP address of the requester was not mentioned in the list of hosts allowed to issue / request SNMP MIB objects information. Remote attacker could use this flaw to gain host related sensitive information via performing a SNMP query.

References: http://bugs.gentoo.org/showbug.cgi?id=250429

Upstream patch: http://net-snmp.svn.sourceforge.net/viewvc/net-snmp?view=rev&revision=17367

CERT has told us of an authentication bypass flaw in Net-SNMP and UCD-SNMP.

According to net-snmp:

"The quick technical summary is that the SNMPv3 packet contains a truncated HMAC authentication code. The author that wrote the code very very long ago to check that HMAC code used the length of the packet's version of the HMAC code to do the check. Thus if you send a single byte HMAC code, it'll only check it against the first byte of HMAC output. Thus it's fairly easy to spoof an authenticated SNMPv3 packet."