What’s Vulnerable › Vulnerabilities

CVE-2026-89147: Net-SNMP through 5.9.5.2 Denial of Service via Blocking Unauthenticated SMUX Read

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-11 · updated 2026-09-24
• Weakness: CWE-400

Description

Net-SNMP through 5.9.5.2 contains a denial of service vulnerability in the SMUX module where smux_accept() 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 products

• net-snmp: through 5.9.5.2

References

• https://gist.github.com/thesmartshadow/001cea595e75fed6aaea7389666dc9eb
• https://github.com/net-snmp/net-snmp
• https://github.com/net-snmp/net-snmp/blob/v5.9.5.2/agent/mibgroup/smux/smux.c
• https://www.vulncheck.com/advisories/net-snmp-through-5.9.5.2-denial-of-service-via-blocking-unauthenticated-smux-read
• https://gist.github.com/thesmartshadow/001cea595e75fed6aaea7389666dc9eb

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