Cisco Snort 3 Vulnerability Leading to Sensitive Data Disclosure

Cisco has disclosed two critical vulnerabilities in the Snort 3 detection engine affecting multiple enterprise security products, including firewalls, threat defense systems, and edge platforms.

The vulnerabilities, tracked as CVE-2026-20026 and CVE-2026-20027 under advisory cisco-sa-snort3-dcerpc-vulns-J9HNF4tH, could allow unauthenticated remote attackers to leak sensitive information or cause denial-of-service conditions by disrupting packet inspection capabilities.

The vulnerabilities stem from improper buffer handling logic when processing Distributed Computing Environment Remote Procedure Call (DCE/RPC) requests.

The first vulnerability, CVE-2026-20026, involves a buffer use-after-free condition that could enable attackers to trigger unexpected engine restarts, interrupting critical packet inspection operations.

The second, CVE-2026-20027, exploits an out-of-bounds read vulnerability that permits attackers to extract sensitive information from the Snort 3 data stream.

Both vulnerabilities carry a Medium severity rating, with CVSS base scores of 5.8 and 5.3, respectively, indicating network-accessible attack vectors requiring no authentication or user interaction.

The vulnerability exposure extends across Cisco’s extensive security portfolio. Open Source Snort 3 deployments require immediate patching to version 3.9.6.0.

Cisco Secure Firewall Threat Defense (FTD) systems running Snort 3 face exposure; notes new FTD installations from version 7.0.0 onward run Snort 3 by default, while upgraded systems from earlier releases continue running Snort 2.

Cisco IOS XE-based security products, including the Catalyst 8000 and 8500 series edge platforms and Integrated Services Routers, are affected if the optional Unified Threat Defense module is installed and enabled.

Cisco Snort 3 Vulnerability

Additionally, Cisco Meraki MX series appliances across various models from the MX67 through the MX600 and virtual variants remain vulnerable until patches scheduled for February 2026 are applied.

Exploitation requires attackers to send a large volume of crafted DCE/RPC requests through an established connection monitored by Snort 3.

Comprehensive fixes: Snort 3.9.6.0 for open-source deployments, hotfixes for FTD versions 7.0 and 7.2 available through the Software Center, and updates for Cisco IOS XE scheduled for version 26.1.1 in February 2026.

While this represents a meaningful technical barrier compared to more straightforward attacks, the ability to leak sensitive information or turn off inspection mechanisms poses significant risk to network defense.

Cisco explicitly notes that no workarounds currently exist to mitigate these vulnerabilities, mandating software updates as the sole remediation path.

Organizations running affected products should consult Cisco’s Software Checker tool to identify exposure and prioritize patch deployment.

The Cisco Product Security Incident Response Team confirms no active exploitation or public disclosure at the time of advisory publication, providing a window for orderly remediation across affected infrastructure.

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