CVE-2025-20175: Cisco IOS SNMP DoS Vulnerability

CVE-2025-20175 Overview

A vulnerability in the SNMP subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to cause a Denial of Service (DoS) condition on affected devices. This vulnerability is due to improper error handling when parsing SNMP requests. An attacker could exploit this vulnerability by sending a crafted SNMP request to an affected device, causing the device to reload unexpectedly and resulting in service disruption.

The vulnerability affects SNMP versions 1, 2c, and 3. To exploit this vulnerability through SNMP v2c or earlier, the attacker must know a valid read-write or read-only SNMP community string for the affected system. To exploit this vulnerability through SNMP v3, the attacker must have valid SNMP user credentials for the affected system.

Critical Impact

Successful exploitation allows authenticated remote attackers to cause affected Cisco network devices to reload unexpectedly, resulting in network outages and denial of service conditions across enterprise infrastructure.

Affected Products

• Cisco IOS Software (multiple versions from 12.2 through 15.9)
• Cisco IOS XE Software (versions 3.2.x through 17.16.x)

Discovery Timeline

• February 5, 2025 - CVE CVE-2025-20175 published to NVD
• July 3, 2025 - Last updated in NVD database

Technical Details for CVE-2025-20175

Vulnerability Analysis

This vulnerability exists within the SNMP subsystem of Cisco IOS and IOS XE Software, which is responsible for network management and monitoring functions. The SNMP subsystem processes incoming SNMP requests for device status, configuration, and management operations. When the vulnerable code encounters a specially crafted SNMP request, improper error handling in the parsing routines causes the device to reload, resulting in a denial of service condition.

The vulnerability is particularly concerning because SNMP is widely deployed in enterprise networks for device monitoring and management. While authentication is required to exploit this vulnerability, SNMP community strings are often weakly configured or inadvertently exposed in many organizations.

Root Cause

The root cause of this vulnerability is improper error handling when parsing SNMP requests (CWE-805: Buffer Access with Incorrect Length Value). The SNMP parsing code fails to properly validate and handle certain malformed or crafted SNMP request data, leading to an unhandled condition that triggers a device reload.

Attack Vector

The attack vector is network-based and requires authentication. An attacker must have network access to the SNMP service on the affected device and possess valid SNMP credentials. The attack can be executed as follows:

1. The attacker identifies a Cisco device running vulnerable IOS or IOS XE software with SNMP enabled
2. The attacker obtains valid SNMP community strings (for SNMPv1/v2c) or user credentials (for SNMPv3)
3. The attacker crafts a malicious SNMP request designed to trigger the parsing error
4. Upon receiving and processing the crafted request, the device experiences an unhandled error condition
5. The device reloads unexpectedly, causing service disruption to all traffic passing through the device

The vulnerability can be triggered using any of the three SNMP versions. For SNMPv1 and SNMPv2c, knowledge of a valid community string (read-only or read-write) is sufficient. For SNMPv3, valid user credentials are required.

Detection Methods for CVE-2025-20175

Indicators of Compromise

• Unexpected device reloads with crash information pointing to SNMP subsystem processes
• Syslog messages indicating SNMP-related process crashes or exceptions
• High frequency of SNMP requests from unusual source IP addresses preceding device restarts
• Crash dump files referencing SNMP parsing or request handling functions

Detection Strategies

• Monitor for unusual patterns of device reloads, particularly multiple devices reloading within short time periods
• Implement SNMP traffic analysis to detect malformed or unusual SNMP request patterns
• Configure syslog forwarding to centralized logging systems to correlate SNMP-related events across multiple devices
• Deploy network intrusion detection systems (IDS) with signatures for known SNMP exploitation patterns

Monitoring Recommendations

• Enable detailed SNMP logging on network devices to capture request sources and types
• Implement baseline monitoring for device reload frequency and correlate with SNMP activity
• Configure alerting for any SNMP authentication failures followed by successful authentications from the same source
• Review crashinfo files on affected devices for patterns indicating exploitation attempts

How to Mitigate CVE-2025-20175

Immediate Actions Required

• Review the Cisco Security Advisory for specific patched software versions
• Inventory all Cisco IOS and IOS XE devices in the environment and identify vulnerable versions
• Implement access control lists (ACLs) to restrict SNMP access to only authorized management stations
• Consider disabling SNMP on devices where it is not operationally required

Patch Information

Cisco has released software updates addressing this vulnerability. Organizations should consult the Cisco Security Advisory for detailed information on fixed software releases and upgrade recommendations specific to their deployed software versions.

Workarounds

• Implement SNMP access control lists to restrict SNMP traffic to trusted management IP addresses only
• Use SNMPv3 with strong authentication and encryption instead of SNMPv1/v2c community strings
• Disable SNMP on network devices where it is not required for operational purposes
• Implement network segmentation to isolate management traffic from general network traffic

# Example SNMP ACL configuration to restrict access
access-list 10 permit 10.0.0.0 0.0.0.255
snmp-server community <community-string> RO 10
snmp-server community <community-string> RW 10