Known exploited vulnerability · CISA KEV

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

Cisco IOS and IOS XE contains a stack-based buffer overflow vulnerability in the Simple Network Management Protocol (SNMP) subsystem that could allow for denial of service or remote code execution. 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.

CVE-2025-20352

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2025-09-29: attackers are using it right now.

CISA KEV: Listed; Added 2025-09-29 · federal fix-by 2025-10-20
EPSS (30 days): 42%; Higher than 99% of CVEs · 2026-11-01
CVSS v3.1: 7.7 High; CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

What CISA says

Cisco IOS and IOS XE Software SNMP Denial of Service and Remote Code Execution Vulnerability

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

NVD description · published 2025-09-24

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 all

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How to check if you are exposed to CVE-2025-20352

Find every Cisco IOS and IOS XE system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2025-20352.

US federal agencies had to fix this by 2025-10-20. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2025-20352. Check the vendor advisory for the exact fixed builds before you sign anything off.

Product	Vulnerable versions
Cisco IOS XE	3.5.0e; 3.5.0sq; 3.5.1e; 3.5.1sq; 3.5.2e; 3.5.2sq and 343 more
Cisco IOS	12.2(33)sxi; 12.2(33)sxi1; 12.2(33)sxi2; 12.2(33)sxi2a; 12.2(33)sxi3; 12.2(33)sxi4 and 720 more
Cisco IOS XE Sd-Wan	16.9.1; 16.9.2; 16.9.3; 16.9.4; 16.10.1; 16.10.2 and 15 more

Timeline

2025-09-24 · Published in the National Vulnerability Database
2025-09-29 · Added to CISA's Known Exploited Vulnerabilities catalog, 5 days after it was published
2025-10-20 · Fix-by date for US federal agencies, passed 377 days ago

Vendor advisories and fixes

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snmp-x4LPhte

Weakness type

CWE-121

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Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.