# CVE-2026-20124: Cisco IOS XE SNMP denial of service in error handling

Source: https://junglewise.ai/threats/cve-2026-20124-cisco-ios-xe-snmp-denial-of-service-in-error-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-05. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-20124 · Severity: high · CVSS 7.7 · Published 2026-08-05

A vulnerability in Cisco IOS XE's SNMP subsystem can be exploited by an authenticated attacker with SNMP credentials to crash the network device, causing temporary unavailability. An attacker with valid SNMP community strings or user credentials can send a specially crafted SNMP request that triggers improper error handling, forcing the affected device to reload. This impacts network availability and could disrupt critical operations on affected routers or switches.

Technologies: [Cisco IOS XE Software](https://junglewise.ai/threats/technologies/ios-xe-software). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20124 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20124 being exploited in the wild.

**How severe is CVE-2026-20124?** High severity, with a CVSS score of 7.7, published 5 August 2026.

**Which products and versions are affected?** Cisco IOS XE Software <UNKNOWN>.

**Is there a fix for CVE-2026-20124?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20124 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-20124?** Check whether you run Cisco IOS XE Software at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a denial of service flaw (CWE-772) in the SNMP subsystem's error handling logic when parsing malformed SNMP requests. It affects all SNMP versions (1, 2c, and 3). An attacker must be authenticated with valid SNMPv1/v2c community strings (read-only or read-write) or valid SNMPv3 user credentials to exploit this vulnerability. The attack vector is network-based, and a successful exploit causes an unexpected device reload. Cisco has released software patches; no workarounds are available, though temporary mitigation via OID exclusion is possible.

## Affected products

- Cisco IOS XE Software <UNKNOWN>

## Timeline

- 2026-08-05: disclosed: Cisco security advisory published
- 2026-08-05: other: Cisco Bug ID CSCws90638

## References

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

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