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Two newly disclosed Snort 3 vulnerabilities allow unauthenticated attackers to disrupt inspection or leak sensitive data using crafted network traffic.
Because Snort 3 is widely deployed across Cisco security products, the vulnerabilities affect a broad range of organizations that rely on network-based threat detection.
The vulnerabilities “… could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to leak sensitive information or to restart, which would result in an interruption of packet inspection,” said Cisco in its advisory.
What’s Affected by the Snort 3 Vulnerabilities
The vulnerabilities affect Cisco Secure Firewall Threat Defense (FTD) software, open-source Snort 3, Cisco IOS XE software with Unified Threat Defense (UTD), and multiple Cisco Meraki appliances.
Organizations running Secure FTD versions 7.0.0 and later face elevated risk because Snort 3 operates as the default inspection engine in those releases.
Cisco identified the issues while analyzing how Snort 3 processes Distributed Computing Environment and Remote Procedure Call (DCE/RPC) traffic.
When the detection engine handles a high volume of these requests, flaws in its buffer management logic can be triggered.
The first vulnerability, CVE-2026-20026, is a use-after-free condition in the engine’s buffer processing code.
Exploiting it can cause Snort 3 to restart unexpectedly, resulting in denial-of-service conditions that temporarily disable packet inspection.
The second issue, CVE-2026-20027, is an out-of-bounds read flaw that allows attackers to extract data from memory adjacent to allocated buffers.
This vulnerability can expose sensitive network traffic passing through the inspection engine, including internal metadata or credentials.
In both cases, an attacker sends a series of specially crafted DCE/RPC requests over an established connection. The traffic itself does not need to be overtly malicious, making detection difficult.
While Cisco has not reported active exploitation at this time, the simplicity of the attack path and lack of authentication requirements increase the likelihood that proof-of-concept exploits will emerge.
Securing Network Inspection Infrastructure
Addressing these Snort 3 vulnerabilities requires more than applying a single patch, as inspection engines sit at a critical control point in the network.
Organizations should assume that attackers may target detection infrastructure directly and plan accordingly.
The following mitigations focus on reducing exposure, limiting blast radius, and maintaining visibility even if inspection services are disrupted.
- Upgrade immediately to patched versions, including Snort 3.9.6.0 and applicable Cisco Secure FTD hot fixes, and validate that inspection resumes correctly after updates.
- Reduce exposure to DCE/RPC by blocking unnecessary traffic at network boundaries and disabling protocol inspection where it is not required.
- Limit attack impact through network segmentation, least-privilege configurations, and isolating inspection engines from sensitive control planes.
- Apply upstream controls such as rate limiting and access restrictions to prevent high-volume or malformed traffic from reaching inspection engines.
- Monitor continuously for abnormal Snort behavior, including crashes, repeated restarts, memory anomalies, and inspection gaps, and regularly test incident response plans.
- Design for resilience using high-availability or failover configurations to ensure visibility is maintained or quickly restored during inspection engine failures.
Vulnerabilities in detection engines can create blind spots just as damaging as flaws in production workloads if left unaddressed.
By combining timely patching with layered defenses and resilience planning, organizations can reduce both the likelihood and impact of exploitation.
These Snort 3 vulnerabilities underscore a persistent challenge in cybersecurity: weaknesses in defensive tools can be just as disruptive as flaws in the systems they are designed to protect.
Network inspection engines sit at a critical enforcement point, and as they grow more complex and process increasingly high volumes of traffic, even minor memory-handling errors can have far-reaching consequences.
When these components fail, organizations may lose visibility, expose sensitive data, or create silent gaps in detection. The result is risk that extends well beyond a single device, affecting the integrity of entire network security architectures.
To address this kind of systemic risk, many organizations are turning to zero-trust solutions that reduce reliance on any single control and assume failure as a baseline.
