Zero-Day Vulnerability Exploited in Cisco IOS and IOS XE SNMP (CVE-2025-20352)
October 2nd, 2025
High
Our Cyber Threat Intelligence Unit is monitoring CVE-2025-20352, a recently disclosed and actively exploited zero-day vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE. The vulnerability allows attackers to either crash affected devices or, under specific conditions, gain complete control with root privileges. Since SNMP is widely used for device monitoring, exposed or misconfigured deployments can be abused. With compromised SNMP credentials, attackers can send crafted SNMP packets that destabilize devices or, where admin rights are present, enable the takeover of core infrastructure. Exploitation has already been observed in the wild, affecting popular platforms like Meraki MS390 and Catalyst 9300 series switches. The risk is particularly high for enterprises and service providers that rely on Cisco network infrastructure. A successful exploit can cause network outages, facilitate lateral movement, and result in the loss of administrative control.
Technical Details
Attack Type: Remote Code Execution (RCE) and Denial of Service (DoS) via SNMP stack overflow.
Severity: High (CVSS 7.7).
Delivery Method: Crafted SNMP packets sent from remote hosts; requires valid SNMP credentials.
Infrastructure: Exploitation observed following compromise of local administrative credentials.
Evasion & Techniques:
Abuse of legitimate SNMP access over IPv4/IPv6.
Stack overflow triggered by malformed SNMP packets targeting vulnerable Object Identifiers (OIDs).
Attempts to bypass weak or misconfigured SNMP restrictions.
Permissions Required: DoS requires SNMP read access; RCE requires SNMP plus admin (priv-15) rights.
Affected Platforms: Cisco IOS, IOS XE, Meraki MS390, and Catalyst 9300 (running vulnerable software trains).
Impact
Device Compromise: RCE with root privileges under administrative conditions.
Denial of Service: Forced reloads or crashes through malformed SNMP packets.
Network Disruption: Potential network outages from compromised or unstable infrastructure.
Operational Risks: Opportunity for lateral movement, data exfiltration, or persistent backdoors once network infrastructure is controlled.
Detection Method
Network & SNMP Logs: Monitor for malformed or anomalous SNMP traffic, including unexpected packet sizes or community strings.
Device Monitoring: Track unexplained reboots, crashes, or reloads correlated with SNMP activity.
Security Tools: Use vulnerability scanners (e.g., Qualys QID 317727) to identify vulnerable devices and firmware versions.
Threat Hunting: Look for patterns of SNMP probing, failed authentication attempts, or abnormal IPv4/IPv6 SNMP traffic.
Mitigation Monitoring: If using Cisco’s temporary mitigation (snmp-server view restrictions), validate that OIDs are blocked as expected.
Indicators of Compromise
There are No Indicators of Compromise (IOCs) for this Advisory.
Recommendations
Patch Management: Apply fixed releases provided by Cisco’s advisory / Software Checker. Do not rely on version assumptions; confirm for your platform. There are no workarounds beyond mitigations.
Mitigations (until patched): Restrict SNMP to trusted IPs, limit access with snmp-server view to exclude vulnerable OIDs, and disable SNMP if not operationally required.
Access Control: Enforce SNMPv3 with strong authentication and encryption. Eliminate legacy SNMPv1/v2c where possible.
Monitoring & Logging: Enable detailed SNMP logging and correlate anomalies with traffic or device behavior.
Incident Response: Immediately isolate suspected compromised devices and perform forensic analysis if exploitation is suspected.
Awareness: Train network admins on risks of misconfigured SNMP and enforce hardened configurations.
Conclusion
CVE-2025-20352 poses a serious threat to enterprise network infrastructure. Exploitation has been confirmed in the wild, with adversaries leveraging valid SNMP credentials to trigger device reloads or achieve root-level code execution. In environments where Cisco IOS and IOS XE devices support connectivity, even one compromised device can trigger widespread outages and provide attackers a valuable foothold. We urge organizations to prioritize patching, enforce SNMP hardening, and monitor for anomalous traffic to reduce the risk of widespread compromise and operational disruption.