Cisco Security Advisoriescisco-sa-iosxe-snmp-dos-ZAqNm4MD

Cisco IOS XE Software SNMP Denial of Service Vulnerability

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to improper error handling when parsing SNMP requests. This vulnerability affects all versions of SNMP - Versions 1, 2c, and 3. An attacker could exploit this vulnerability by sending a malformed SNMP request to an affected device. A successful exploit could allow the attacker to cause the device to reload unexpectedly. The attacker must have the SNMPv1 or v2c read-only or read-write community string or valid SNMPv3 user credentials on the affected device. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. There is a mitigation that addresses this vulnerability. This advisory is available at the following link:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-snmp-dos-ZAqNm4MD Security Impact Rating: High CVE: CVE-2026-20124

Read the vendor bulletin

HighCVSS not listedHigh severity

Scope

What the vendor says is affected

The collected bulletin did not provide a separate affected-products list. Check the original bulletin before making an exposure decision.

Next step

What the vendor recommends

Cisco has released software updates that address this vulnerability.

Review the complete instructions on the vendor's site

Timeline

When this advisory changed

Aug 5, 2026 at 4:00 PM UTC
Published by Cisco
The publication date reported by the vendor.
Aug 20, 2026 at 2:20 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Aug 26, 2026 at 3:50 PM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-20124View CVSS, KEV, EPSS, and threat context

Source

Start with the vendor's bulletin

SecurityAlert organizes the fields the vendor published. The original bulletin remains the source of record for affected versions, fixes, and later changes.

Vendor: Cisco
Advisory ID: cisco-sa-iosxe-snmp-dos-ZAqNm4MD
Last source check: Sep 13, 2026 at 5:10 AM UTC

Open the official bulletin How SecurityAlert builds this record

Your environment

Check the systems you actually run

A vendor advisory can tell you what may be affected. It cannot tell you whether that product and version are installed in your environment.

Confirm the product and installed version.
Read the vendor's prerequisites and exceptions.
Test the update or mitigation through your normal change process.

Keep following

Get new Cisco advisories

Use the vendor-specific RSS feed or set up alerts for a product your team relies on.

Follow this vendor's RSS feed

What the vendor says is affected

What the vendor recommends

When this advisory changed

CVEs named in this advisory

Related advisories from Cisco

Cisco Advance Notification for Publication of August 5, 2026, Security Advisories

Cisco IOS XR Software Security Hardening Release: September 2026

Cisco Secure Firewall Management Center Software Authentication Bypass Vulnerability

Cisco Advance Notification for Publication of September 16, 2026, Security Advisories

Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability

Cisco Secure Email Secure/Multipurpose Internet Mail Extensions Ciphertext Decryption Vulnerabilities