Cisco’s SNMPv3 Truncation Trouble: When Your ACL Goes MIA!
In the May 2025 release of the Cisco IOS and IOS XE Software Security Advisory, a quirk was discovered: SNMPv3 configurations on Cisco devices might get their access lists clipped like a bad haircut if the configuration line exceeds 255 characters. Administrators, beware—your ACL might go from “secure” to “surprise!”
Hot Take:
Well, well, well, Cisco users, it seems like your network configuration has taken a turn for the comedic. In a move that can only be described as “character limiting gone wild,” the SNMPv3 feature has decided that 255 characters are all your configuration needs. Anything more, and it’s like leaving a limerick unfinished—sad and missing its punchline. It’s a classic case of “my router ate my homework,” and the punchline is an unsecured network.
Key Points:
– Cisco IOS and IOS XE Software have a vulnerability affecting devices if SNMPv3 is configured.
– Configuration lines longer than 255 characters are truncated, affecting ACL names.
– No ACL enforcement means SNMPv3 users are left without access control.
– The vulnerability affects all releases of Cisco IOS and IOS XE.
– Admins can use the `show snmp user` command to verify configuration issues.