# CVE-2026-20179: Cisco Snort 3 GRE detection engine denial of service

Source: https://junglewise.ai/threats/cve-2026-20179-multiple-cisco-products-are-affected-by-a-vulnerability-in-the  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-20179 · Severity: medium · CVSS 5.8 · Published 2026-10-21

Snort 3 is a network intrusion detection and prevention engine used to inspect packet traffic on firewalls and routers. A vulnerability in its GRE packet parsing can be exploited remotely to crash the detection engine, causing traffic inspection to stop temporarily. This results in a denial of service where the firewall cannot protect the network during the outage.

Technologies: [Cisco IOS XE Software](https://junglewise.ai/threats/technologies/ios-xe-software), [Cisco Meraki MX Security Appliances](https://junglewise.ai/threats/technologies/meraki-mx-security-appliances), [Cisco Secure Firewall Threat Defense Software](https://junglewise.ai/threats/technologies/firepower-threat-defense-software), [Cisco Snort 3](https://junglewise.ai/threats/technologies/snort-3). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20179 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20179 being exploited in the wild.

**How severe is CVE-2026-20179?** Medium severity, with a CVSS score of 5.8, published 21 October 2026.

**Which products and versions are affected?** Cisco IOS XE Software releases with Unified Threat Defense (UTD) Snort IPS Engine.

**Is there a fix for CVE-2026-20179?** No fixed version is recorded yet. No workarounds are available; upgrade to patched software versions.</anigation>
</invoke> 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-2026-20179 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20179?** Check whether you run Cisco IOS XE Software, Cisco Meraki MX Security Appliances, Cisco Secure Firewall Threat Defense Software or one of the others listed 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.

## How to fix


No workarounds are available; upgrade to patched software versions.</anigation>
</invoke>

## Technical details

The vulnerability stems from incomplete error checking in Snort 3's Generic Routing Encapsulation (GRE) packet parser, allowing an unauthenticated, remote attacker to send a crafted GRE packet that triggers an unexpected restart of the detection engine. An attacker can cause service interruption by exploiting this over the network without authentication or user interaction. Cisco has released patches; no workarounds are available.

## Affected products

- Cisco Snort 3
- Cisco Secure Firewall Threat Defense Software
- Cisco IOS XE Software releases with Unified Threat Defense (UTD) Snort IPS Engine
- Cisco Meraki MX Security Appliances

## Timeline

- 2026-10-21: disclosed

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-misc-dos-6mB22qAK](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-misc-dos-6mB22qAK)

## Related threats

- [Cisco Snort 3 memory management denial of service](https://junglewise.ai/threats/cve-2026-76489-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Snort 3 Detection Engine denial of service in GTP codec](https://junglewise.ai/threats/cve-2026-76445-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Snort 3 uncontrolled resource consumption](https://junglewise.ai/threats/cve-2026-20356-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)
- [Cisco Snort 3 improper privilege management](https://junglewise.ai/threats/cve-2026-20291-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)
- [Cisco Snort 3 incorrect calculation vulnerability](https://junglewise.ai/threats/cve-2026-20236-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)