CVE-2026-20124
Received Received - Intake

Denial of Service in Cisco IOS XE via Malformed SNMP Request

Publication date: 2026-08-05

Last updated on: 2026-08-05

Assigner: Cisco Systems, Inc.

Description
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.

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Meta Information

Published
2026-08-05
Last Modified
2026-08-05
Generated
2026-08-05
AI Q&A
2026-08-05
EPSS Evaluated
N/A
NVD
CVE-2026-20124
EUVD
EUVD-2026-53449

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
cisco ios_xe to 3 (exc)
cisco ios_xe to 3.0.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-772 The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

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Executive Summary

This vulnerability is in the SNMP subsystem of Cisco IOS XE Software. It allows an authenticated remote attacker to cause an affected device to reload by sending a malformed SNMP request. This happens due to improper error handling when parsing SNMP requests.

Detection Guidance

Detecting this vulnerability requires monitoring for malformed SNMP requests or unexpected device reloads. Check SNMP logs for unusual activity or errors in parsing requests. Use network monitoring tools to inspect SNMP traffic for malformed packets. Commands like 'show snmp' or 'show logging' on Cisco devices may help identify issues.

Impact Analysis

An attacker could exploit this to cause a denial of service by making the device reload unexpectedly. The attacker needs valid SNMP credentials or community strings to send the malicious request.

Compliance Impact

This vulnerability primarily causes denial of service (DoS) conditions by forcing affected Cisco IOS XE devices to reload unexpectedly. While not directly violating GDPR or HIPAA, such disruptions could impact systems handling regulated data, potentially leading to service unavailability or data processing delays that may violate availability requirements under these standards.

Mitigation Strategies

Immediately restrict SNMP access to trusted sources only. Disable SNMP if not required. Update to the latest Cisco IOS XE Software version. Ensure strong SNMP community strings or v3 credentials are used. Monitor devices for unexpected reloads or crashes.

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