CVE-2025-20352: Cisco IOS and IOS XE Software SNMP Denial of Service and Remote Code Execution Vulnerability

Vulnerability summary

CVE-2025-20352 is a high (CVSS 7.7) Stack-based Buffer Overflow vulnerability in Cisco IOS and IOS XE. It is known to be exploited: CISA lists it, first on 29-09-2025. EPSS estimates a 41.50% chance of exploitation in the next 30 days, higher than 98.6% of scored vulnerabilities.

Timeline

1. 24-09-2025
   PublishedVulnerability first disclosed.
2. 29-09-2025
   Added to CISA KEVCisco IOS and IOS XE Software SNMP Denial of Service and Remote Code Execution Vulnerability
3. 20-10-2025
   CISA remediation dueApply mitigations per vendor instructions.
4. 26-02-2026
   Last modifiedVulnerability information updated.

Description

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow the following: An authenticated, remote attacker with low privileges could cause a denial of service (DoS) condition on an affected device that is running Cisco IOS Software or Cisco IOS XE Software. To cause the DoS, the attacker must have the SNMPv2c or earlier read-only community string or valid SNMPv3 user credentials. An authenticated, remote attacker with high privileges could execute code as the root user on an affected device that is running Cisco IOS XE Software. To execute code as the root user, the attacker must have the SNMPv1 or v2c read-only community string or valid SNMPv3 user credentials and administrative or privilege 15 credentials on the affected device. An attacker could exploit this vulnerability by sending a crafted SNMP packet to an affected device over IPv4 or IPv6 networks. This vulnerability is due to a stack overflow condition in the SNMP subsystem of the affected software. A successful exploit could allow a low-privileged attacker to cause the affected system to reload, resulting in a DoS condition, or allow a high-privileged attacker to execute arbitrary code as the root user and obtain full control of the affected system. Note: This vulnerability affects all versions of SNMP.

• CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).