Summary

• A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS XE Software 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 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.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. However, there is a mitigation.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snmpwred-x3MJyf5M

  This advisory is part of the September 2025 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2025 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco switches if they are running a vulnerable release of Cisco IOS XE Software and if they have the weighted early random detection (WRED) for Multiprotocol Label Switching (MPLS) experimental field (EXP) configured and the SNMP feature enabled. This vulnerability affects all versions of SNMP (versions 1, 2c, and 3). 

  Note: Cisco routing platforms that run Cisco IOS XE Software do not support WRED for MPLS EXP, so they are not affected by this vulnerability.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Determine the WRED for MPLS EXP Configuration

  To determine whether a device has WRED for MPLS EXP configured, use the show running-config CLI command and check for the presence of the random-detect mpls-exp-based command under an applied policy. If there is output and that class is part of an applied policy-map, as shown in the following example, the device is considered vulnerable:

  Switch# show running-config
  policy-map TEST
   class class-default
    random-detect mpls-exp-based
  !
  interface GigabitEthernet 1/0/48
   service-policy output TEST

  If the device does not have WRED for MPLS EXP configured, it is not affected by this vulnerability.

  Determine the SNMP Configuration

  To determine whether a device has SNMPv1 or v2c enabled, use the show running-config | include snmp-server community CLI command. If there is output, SNMP is enabled, as shown in the following example:

  Switch# show running-config | include snmp-server community
  snmp-server community public ro

  To determine whether a device has SNMPv3 enabled, use the show running-config | include snmp-server group and show snmp user CLI commands. If there is output from both commands, SNMPv3 is enabled, as shown in the following example:

  Switch# show running-config | include snmp-server group
  snmp-server group v3group v3 noauth
  
  Switch# show snmp user
  User name: remoteuser1
  Engine ID: 800000090300EE01E71C178C
  storage-type: nonvolatile     active
  Authentication Protocol: SHA
  Privacy Protocol: None
  Group-name: v3group   

   

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect the following Cisco products:

  • IOS Software
  • IOS XR Software
  • NX-OS Software

Workarounds

• There are no workarounds that address this vulnerability. However, as a mitigation, administrators can disable the vulnerable object identifier (OID) on a device.

  Disable the Affected OID

  As a best practice, SNMP access should be allowed only from trusted network devices. For configuration options, see Secure Your Simple Network Management Protocol.

  To disable the OID, complete the following steps:

  1. Create an SNMP view with the standard security configurations.

  snmp-server view SNMP_DOS iso included
  snmp-server view SNMP_DOS snmpUsmMIB excluded
  snmp-server view SNMP_DOS snmpVacmMIB excluded
  snmp-server view SNMP_DOS snmpCommunityMIB excluded

  2. Exclude the vulnerable OID from the SNMP view.

  snmp-server view SNMP_DOS cbQosREDClassStatsEntry excluded 

  While this mitigation has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

• Cisco considers any workarounds and mitigations to be temporary solutions until an upgrade to a fixed software release is available. To fully remediate this vulnerability and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.

  Cisco IOS and IOS XE Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”). 

  To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to determine whether a release is affected by any Cisco Security Advisory. To use the form, follow these steps:

  1. Choose which advisories the tool will search—only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
  2. Enter a release number—for example, 15.9(3)M2 or 17.3.3.
  3. Click Check.

   

  Only this advisory All Critical and High advisories All advisories

   

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Source

• This vulnerability was found during the resolution of a Cisco Technical Assistance Center (TAC) support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snmpwred-x3MJyf5M

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2025-SEP-24

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