SNMP typically isn't the most loved protocol when it comes to security, most of this stems from the older versions.  The current version (SNMPv3) has a way to do authentication using a keyed-Hash Message Authentication Code (HMAC) HMAC.

It seems CERT is coordinating a vulnerability regarding this: "Implementations of SNMPv3 may allow a shortened HMAC code in the authenticator field to authenticate to an agent or a trap daemon using a minimum HMAC of 1 byte." Which obviously isn't the right thing to do.

Cisco has a security advisory on the topic, as will other vendors without much doubt.

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Swa Frantzen -- Gorilla Security