CVE-2025-20171:Cisco IOS and Cisco IOS XE Software contain a SNMP subsystem vulnerability (CVE-2025-20171) that could allow an authenticated, remote attacker to cause a DoS condition on an affected device by sending crafted SNMP requests, potentially causing the device to reload. The issue affects SNMP versions 1, 2c, and 3, with exploitation requiring valid credentials depending on the SNMP version used.

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This vulnerability stems from improper error handling when parsing SNMP requests in Cisco IOS and IOS XE Software. A crafted SNMP request can trigger an uncaught exception, causing the targeted device to reload and resulting in a Denial of Service. The impact is independent of data confidentiality or integrity, primarily affecting availability. Exploitation requires authentication: for SNMP v1/v2c, a valid read-only or read-write community string is needed, while for SNMP v3, valid user credentials are required. The advisory lists a broad set of affected releases across Cisco IOS and IOS XE, ranging from older 12.x versions to newer 16.x branches. The CVSS v3.1 base score is 7.7 (HIGH), with network access as the attack vector, low attack complexity, and no user interaction, but with a changed scope and a high impact to availability. Cisco PSIRT notes that there are no known instances of exploitation at the time of the advisory.

Overview

This CVE describes a DoS vulnerability in the SNMP subsystem of Cisco IOS and IOS XE caused by improper error handling when processing SNMP requests. An authenticated attacker, depending on the SNMP version, can trigger a device reload by issuing a crafted SNMP request, leading to a denial of service. Affected releases cover a wide range of Cisco IOS and IOS XE versions, and exploitation requires valid SNMP credentials for v1/v2c or v3. The vulnerability has a relatively high impact on availability and is categorized with a high severity.

Remediation

  • Upgrade affected devices to a Cisco-recommended fixed release for IOS or IOS XE that addresses this SNMP DoS vulnerability (refer to the Cisco advisory for the exact fixed versions).
  • If immediate upgrading is not feasible, implement compensating controls:
    • Restrict SNMP access to trusted management networks using access control lists (ACLs) and firewall rules.
    • Prefer SNMPv3 with strong authentication and encryption; for SNMP v1/v2c, rotate and tightly manage community strings and limit their exposure.
    • Disable SNMP on devices or interfaces where SNMP is not required.
    • Monitor SNMP traffic and device reload events; enable logging and alerting for SNMP-related errors.
  • After applying mitigations or upgrades, test to ensure SNMP is functioning as intended and that the DoS condition is mitigated.

References

  • Cisco Security Advisory: Cisco Security Advisory cisco-sa-snmp-dos-sdxnSUcW (https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snmp-dos-sdxnSUcW)
  • CVE-2025-20171 – NVD entry (https://nvd.nist.gov/vuln/detail/CVE-2025-20171)

Industry ExposureMost to least
This section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.

  1. Public Administration: Medium
    Public Administration
  2. Manufacturing: Medium
    Manufacturing
  3. Health Care & Social Assistance: Medium
    Health Care & Social Assistance
  4. Educational Services: Medium
    Educational Services
  5. Finance and Insurance: Medium
    Finance and Insurance
  6. Retail Trade: Medium
    Retail Trade
  7. Utilities: Low
    Utilities
  8. Transportation & Warehousing: Low
    Transportation & Warehousing
  9. Professional, Scientific, & Technical Services: Low
    Professional, Scientific, & Technical Services
  10. Other Services (except Public Administration): Low
    Other Services (except Public Administration)
  11. Arts, Entertainment & Recreation: Low
    Arts, Entertainment & Recreation
  12. Management of Companies & Enterprises: Low
    Management of Companies & Enterprises
  13. Real Estate Rental & Leasing: Low
    Real Estate Rental & Leasing
  14. Accommodation & Food Services: Low
    Accommodation & Food Services
  15. Information: Low
    Information
  16. Agriculture, Forestry Fishing & Hunting: Low
    Agriculture, Forestry Fishing & Hunting
  17. Construction: Low
    Construction
  18. Mining: Low
    Mining
  19. Wholesale Trade: Low
    Wholesale Trade
  20. Administrative, Support, Waste Management & Remediation Services: Low
    Administrative, Support, Waste Management & Remediation Services

Focus on What Matters

  1. See Everything.
  2. Identify True Risk.
  3. Proactively Mitigate Threats.

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