Cisco SNMP Zero-Day: Active Exploits Target IOS XE Network Devices in 2025
Executive Summary
In September 2025, Cisco disclosed a critical vulnerability (CVE-2025-20352) affecting its IOS and IOS XE operating systems, actively exploited via the SNMP subsystem. The flaw stems from a stack-based buffer overflow that allows authenticated remote attackers to trigger denial-of-service or potentially achieve root-level remote code execution. Attackers utilized crafted SNMP packets over both IPv4 and IPv6 to compromise devices with SNMP enabled, including popular models like the Meraki MS390 and Catalyst 9300. Cisco confirmed attacks in the wild following credential compromise, urging immediate patching, as no reliable workarounds exist.
This incident highlights the ongoing risks associated with ubiquitous network protocols like SNMP and the necessity of rapid response to zero-day exploits within core infrastructure. The rise of attacks targeting network management systems signals both increased attacker sophistication and heightened regulatory scrutiny.
Why This Matters Now
Organizations face urgent risk as attackers actively exploit a new SNMP vulnerability in Cisco IOS and IOS XE, threatening global network infrastructure. SNMP’s widespread use, the ease of exploitation, and absence of robust mitigations make immediate patching critical to prevent denial-of-service or total compromise.
Attack Path Analysis
Attackers initially exploited exposed SNMP services on unpatched Cisco IOS XE devices by sending crafted packets, resulting in unauthorized access. After obtaining local admin credentials, they escalated privileges, gaining root-level control via the SNMP buffer overflow. With elevated access, attackers moved laterally within the network, targeting additional network devices potentially via internal SNMP or management protocols. Command and control was established through remote code execution, enabling ongoing device management or malware droppers. Though no large-scale data theft was reported, attackers could exfiltrate device configurations or sensitive network information. Ultimately, the attack led to denial of service and could enable future integrity compromises, impacting network availability and business operations.
Kill Chain Progression
Initial Compromise
Description
Attackers exploited a buffer overflow in SNMP on Cisco IOS XE by sending malicious packets to exposed, vulnerable devices, gaining authenticated access.
Related CVEs
CVE-2025-20352
CVSS 8.8A vulnerability in the SNMP subsystem of Cisco IOS and IOS XE Software allows authenticated, remote attackers to cause a denial of service or execute arbitrary code with root-level permissions.
Affected Products:
Cisco IOS – All versions with SNMP enabled
Cisco IOS XE – All versions with SNMP enabled
Exploit Status:
exploited in the wildCVE-2025-20149
CVSS 6.5A vulnerability in the CLI of Cisco IOS and IOS XE Software allows authenticated, local attackers to cause a denial of service condition.
Affected Products:
Cisco IOS – All versions
Cisco IOS XE – All versions
Exploit Status:
proof of conceptCVE-2025-20311
CVSS 7.4A vulnerability in Cisco IOS XE Software for Catalyst 9000 Series Switches allows unauthenticated, adjacent attackers to cause a denial of service condition.
Affected Products:
Cisco IOS XE – All versions for Catalyst 9000 Series Switches
Exploit Status:
no public exploit
MITRE ATT&CK® Techniques
Exploit Public-Facing Application
Valid Accounts
Exploitation for Privilege Escalation
Hardware Additions
Command and Scripting Interpreter
Endpoint Denial of Service
OS Credential Dumping
Potential Compliance Exposure
Mapping incident impact across multiple compliance frameworks.
PCI DSS 4.0 – Security of System Components
Control ID: 6.4.1
NYDFS 23 NYCRR 500 – Cybersecurity Policy
Control ID: 500.03
DORA – ICT Risk Management Framework
Control ID: Art. 8
CISA ZTMM 2.0 – Segmenting Administrative Interfaces
Control ID: Network and Environment Segmentation
NIS2 Directive – Incident Prevention and Response
Control ID: Art. 21(2)d
Sector Implications
Industry-specific impact of the vulnerabilities, including operational, regulatory, and cloud security risks.
Telecommunications
Critical exposure to CVE-2025-20352 SNMP vulnerability in Cisco IOS/XE infrastructure enabling remote code execution and service disruption across network operations.
Financial Services
High-risk SNMP buffer overflow attacks targeting Cisco network devices could compromise payment processing, trading systems, and regulatory compliance requirements.
Health Care / Life Sciences
Network infrastructure vulnerability threatens HIPAA compliance and patient data protection through potential unauthorized access to medical network management systems.
Government Administration
Critical government network infrastructure vulnerable to authenticated remote attacks via SNMP exploitation, risking national security and citizen service disruption.
Sources
- Cisco uncovers new SNMP vulnerability used in attacks on IOS deviceshttps://cyberscoop.com/cisco-ios-xe-snmp-vulnerability-september-2025/Verified
- Cisco IOS XE Software Simple Network Management Protocol Denial of Service Vulnerabilityhttps://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-snmpwred-x3MJyf5M.htmlVerified
- Cisco IOS and IOS XE Software CLI Denial of Service Vulnerabilityhttps://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-ios-cli-EB7cZ6yO.htmlVerified
- Cisco IOS XE Software for Catalyst 9000 Series Switches Denial of Service Vulnerabilityhttps://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-cat9k-PtmD7bgy.htmlVerified
Frequently Asked Questions
Cloud Native Security Fabric Mitigations and ControlsCNSF
Applying Zero Trust segmentation, egress policy enforcement, microsegmentation, and inline threat detection would have contained or blocked attacker exploitation, lateral spread, and outbound channel creation. CNSF-aligned controls can isolate affected infrastructure, monitor abnormal management traffic, and prevent SNMP-based exploits from progressing unchecked.
Control: Zero Trust Segmentation
Mitigation: Unnecessary SNMP exposure to untrusted networks is prevented.
Control: Threat Detection & Anomaly Response
Mitigation: Abnormal privilege escalation attempts are detected in real time.
Control: East-West Traffic Security
Mitigation: Unusual SNMP or admin protocol flows between segments are blocked.
Control: Egress Security & Policy Enforcement
Mitigation: Outbound C2 traffic is restricted and flagged.
Control: Multicloud Visibility & Control
Mitigation: Potential data exfiltration attempts are identified and stopped.
Distributed, inline enforcement helps minimize scope of outages.
Impact at a Glance
Affected Business Functions
- Network Operations
- IT Services
Estimated downtime: 3 days
Estimated loss: $500,000
Potential exposure of network configurations and sensitive operational data due to unauthorized access.
Recommended Actions
Key Takeaways & Next Steps
- • Enforce identity-based Zero Trust segmentation to restrict SNMP management access solely to approved sources.
- • Deploy microsegmentation and east-west controls to contain lateral movement by limiting protocol access between network segments.
- • Implement inline threat detection and anomaly response to quickly surface privilege abuse and SNMP exploitation attempts.
- • Apply strict egress policy enforcement on network devices to monitor and block suspicious outbound connections or exfiltration paths.
- • Maintain centralized, cross-cloud visibility for rapid detection of unauthorized flows and isolation of impacted assets during incidents.
