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High [CVE-2026-20185] Cisco SG350 and SG350X Series Managed Switches SNMP Denial of Service Vulnerability

This high-severity Cisco advisory covers CVE-2026-20185 affecting Small Business Smart and Managed Switches.

cisco-sa-sg350-snmp-dos-GEFZr2Tj Published May 6, 2026Updated by vendor May 6, 2026
CVE-2026-20185
Affected products & platforms
CiscoSwitches
Open vendor advisory

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Summary

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco 350 Series Managed Switches (SG350) and Cisco 350X Series Stackable Managed Switches (SG350X) firmware could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to improper error handling when parsing response data for a specific SNMP request. An attacker could exploit this vulnerability by sending a specific SNMP request to an affected device.

A successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition.

This vulnerability affects SNMP versions 1, 2c, and 3. To exploit this vulnerability through SNMPv2c or earlier, the attacker must know a valid read-write or read-only SNMP community string for the affected system.

Cisco has not released and will not release software updates that address this vulnerability because the affected products are past the date for End of Software Maintenance Releases.

The Cisco Product Security Incident Response Team (PSIRT) will continue to evaluate and disclose security vulnerabilities that affect these products until the Last Date of Support is reached.

However, there is a mitigation.

Affected product named by the advisory: Small Business Smart and Managed Switches.

Affected versions
  • Scope: This vulnerability affects the following Cisco products if they are running Cisco SG350 and SG350X Series Managed Switch Firmware Release 2.5.9.54 or 2.5.9.55 and have two or more 60-watt Power over Ethernet (PoE) ports enabled:

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation checklist

Temporary workarounds
  • There are no workarounds that address this vulnerability. However, as a mitigation, administrators may disable the vulnerable object ID (OID) on a device.
  • To disable and exclude the OID, complete the following steps:
  • 1. Create a new SNMP view excluding the affected OID. Use the following commands:
  • snmp-server view SNMP_DOS iso included
  • snmp-server view SNMP_DOS rlPethPsePortTable excluded
  • 2. Apply the view to the SNMP community or SNMP v3 group:
  • For SNMP v1 or v2c, apply this configuration to all configured community strings. Use the following command:
  • snmp-server community mycomm view SNMP_DOS RO
  • For SNMPv3, apply this to all configured SNMP users. Use the following command:
  • snmp-server group v3group v3 auth read SNMP_DOS write SNMP_DOS

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Discussion(0)

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