Cisco Small Business Smart and Managed Switches 2.5.9.54/2.5.9.55 SNMP Subsystem heap-based overflow

Summaryinfo

A vulnerability has been found in Cisco Small Business Smart and Managed Switches 2.5.9.54/2.5.9.55 and classified as critical. This affects an unknown function of the component SNMP Subsystem. This manipulation causes heap-based overflow. This vulnerability is tracked as CVE-2026-20185. The attack is possible to be carried out remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in Cisco Small Business Smart and Managed Switches 2.5.9.54/2.5.9.55. Affected by this vulnerability is an unknown part of the component SNMP Subsystem. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect availability. The summary by CVE is:

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. To exploit this vulnerability through SNMPv3, the attacker must have valid SNMP user credentials for the affected system.

It is possible to read the advisory at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2026-20185 since 10/08/2025. The exploitation appears to be easy. The attack can be launched remotely. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/06/2026).

Upgrading eliminates this vulnerability.

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Productinfo

Vendor

• Cisco

Name

• Small Business Smart and Managed Switches

Version

• 2.5.9.54
• 2.5.9.55

License

• commercial

Website

• Vendor: https://www.cisco.com/

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