CVE-2026-89147: Net-SNMP through 5.9.5.2 Denial of Service via Blocking Unauthenticated SMUX Read
Net-SNMP through 5.9.5.2 contains a denial of service vulnerability in the SMUX module where smuxaccept() performs an unauthenticated blocking read without timeout on newly accepted connections. An unauthenticated remote client can connect to the SMUX listener and send no data, causing the single-threaded snmpd main loop to block indefinitely and suspend all SNMP processing.
Affected Software
Event History
Frequently Asked Questions
Who is exposed to this issue?
Net-SNMP deployments through 5.9.5.2 that have an accessible SMUX listener are exposed. A remote client can trigger the condition without authentication.
What does an attacker need to do to exploit it?
The attacker only needs network access to connect to the SMUX listener. They can then send no data, leaving the newly accepted connection in a blocking read.
What is the operational impact of a successful attack?
The single-threaded snmpd main loop can block indefinitely. This suspends all SNMP processing, causing a denial of service.