# CVE-2026-20057: Cisco Snort 3 VBA decompression denial of service

Source: https://junglewise.ai/threats/cve-2026-20057-cisco-snort-3-vba-decompression-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-04. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-20057 · Severity: medium · CVSS 5.8 · Published 2026-03-04

Multiple Cisco network security products including Secure Firewall, Threat Defense, and IOS XE routers contain a vulnerability in their Snort 3 intrusion detection engine. An attacker can remotely send specially crafted data to crash the Snort detection engine, causing temporary service outages and leaving networks unprotected from intrusions during the restart period.

Technologies: [Cisco IOS XE](https://junglewise.ai/threats/technologies/ios-xe), [Cisco Secure Firewall Threat Defense](https://junglewise.ai/threats/technologies/firepower-threat-defense), [Cisco Secure Firewall Management Center](https://junglewise.ai/threats/technologies/secure-firewall-management-center), [Cisco Snort 3](https://junglewise.ai/threats/technologies/snort-3). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20057 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20057 being exploited in the wild.

**How severe is CVE-2026-20057?** Medium severity, with a CVSS score of 5.8, published 4 March 2026.

**Which products and versions are affected?** Cisco IOS XE with Unified Threat Defense Snort IPS Engine or UTD Engine for SD-WAN; Cisco Secure Firewall Threat Defense 7.2.0 and later with VBA decompression enabled; Cisco Secure Firewall Management Center 7.2.0 and later; Cisco Snort 3 vulnerable versions documented in fixed software section.

**Is there a fix for CVE-2026-20057?** 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-2026-20057 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20057?** Check whether you run Cisco IOS XE, Cisco Secure Firewall Threat Defense, Cisco Secure Firewall Management Center 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.

## Technical details

This vulnerability exists in the Snort 3 Visual Basic for Applications (VBA) decompression engine and stems from insufficient error checking when processing VBA data. The vulnerability affects multiple CWE classes including CWE-122 (heap-based buffer overflow), CWE-369 (divide by zero), CWE-786 (access of memory location before start of buffer), and CWE-835 (infinite loop). An unauthenticated remote attacker can exploit this by sending a malformed VBA packet to a device running Snort 3 with VBA macro decompression enabled (supported on IMAP, SMTP, HTTP, and POP3 inspectors). A successful exploit causes the Snort 3 Detection Engine to unexpectedly restart, resulting in denial of service. Cisco has released software updates addressing these vulnerabilities, and workarounds are available.

## Affected products

- Cisco Snort 3 vulnerable versions documented in fixed software section
- Cisco Secure Firewall Threat Defense 7.2.0 and later with VBA decompression enabled
- Cisco IOS XE with Unified Threat Defense Snort IPS Engine or UTD Engine for SD-WAN
- Cisco Secure Firewall Management Center 7.2.0 and later

## Timeline

- 2026-03-04: disclosed: Cisco Security Advisory published

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort3-vbavuls-96UcVVed](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort3-vbavuls-96UcVVed)

## 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)