Cisco has disclosed a severe vulnerability in its widely used IOS and IOS XE Software, potentially allowing attackers to crash devices or seize full control through remote code execution.
The flaw, rooted in the Simple Network Management Protocol (SNMP) subsystem, stems from a stack overflow condition that attackers can trigger with a specially crafted SNMP packet over IPv4 or IPv6 networks.
This issue affects all SNMP versions and has already seen exploitation in the wild, highlighting the urgency for network administrators to act swiftly.
The vulnerability enables two main attack vectors. A low-privileged, authenticated remote attacker armed with SNMPv2c read-only community strings or valid SNMPv3 credentials could induce a denial-of-service (DoS) condition, forcing affected devices to reload and disrupting network operations.
More alarmingly, a highly privileged attacker with administrative or privilege level 15 access could execute arbitrary code as the root user on IOS XE devices, granting complete system takeover.
Cisco’s Product Security Incident Response Team (PSIRT) discovered this during a Technical Assistance Center support case, and real-world exploits followed compromised local administrator credentials.
This flaw impacts a broad range of Cisco devices running vulnerable IOS or IOS XE releases with SNMP enabled, including routers, switches, and access points essential to enterprise infrastructures.
Devices that haven’t explicitly excluded the affected object ID (OID) remain at risk. Notably, IOS XR Software and NX-OS Software are unaffected, providing some relief for users of those platforms.
The potential fallout is significant: DoS attacks could halt critical services, while root-level code execution might enable data theft, lateral movement in networks, or deployment of malware.
Given SNMP’s ubiquity for device monitoring, many organizations unwittingly expose themselves by leaving default configurations intact.
Mitigations
Cisco emphasizes that no full workarounds exist, but mitigations can curb immediate threats. Administrators should restrict SNMP access to trusted users only and monitor via the “show snmp host” CLI command.
A key step involves disabling vulnerable OIDs using the “snmp-server view” command to create a restricted view, then applying it to community strings or SNMPv3 groups. For Meraki cloud-managed switches, contacting support is advised to implement these changes.
Patches are now available through Cisco’s September 2025 Semiannual Security Advisory Bundled Publication. Users can verify exposure and find fixed releases using the Cisco Software Checker tool.
To check SNMP status, run CLI commands like “show running-config | include snmp-server community” for v1/v2c or “show snmp user” for v3.
Cisco urges immediate upgrades to fortified software, warning that delays could invite further exploits. As networks grow more interconnected, such vulnerabilities underscore the need for rigorous SNMP hardening and proactive patching.
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