CVE-2026-55401 in Secure Access
Summary
by MITRE • 08/13/2026
CVE-2026-55401 is a null dereference vulnerability on the load-balancing sub-system of Secure Access servers prior to 14.57. Attackers can send an unauthenticated packet to a Secure Access server with load balancing enabled, which results in the internal load balancer crashing. After a successful attack, the Secure Access server is still able to accept connections and is still able to issue a failover to connected clients. https://www.first.org/cvss/calculator/4.0#CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability represents a critical null dereference flaw within the load-balancing subsystem of Secure Access servers running versions prior to 14.57. The vulnerability stems from improper input validation and error handling within the server's internal load balancer component, which fails to properly validate incoming packets before processing them through the load balancing logic. When an attacker sends a specially crafted unauthenticated packet to a vulnerable Secure Access server with load balancing enabled, the system attempts to dereference a null pointer during the packet processing routine, resulting in an immediate crash of the internal load balancer module.
The technical execution of this vulnerability aligns with common software security weaknesses categorized under CWE-476, which specifically addresses null pointer dereference conditions. The attack vector is particularly concerning as it requires no authentication credentials and can be executed remotely over the network, making it accessible to any attacker with basic network connectivity. The CVSS score of 7.3 indicates a high severity impact with low complexity requirements for exploitation, as the vulnerability does not require privileged access or specialized knowledge beyond basic network packet crafting capabilities.
From an operational perspective, while the server remains functional after the crash and can continue accepting new connections, the failure of the load balancing subsystem creates significant availability concerns for services relying on proper load distribution. The system's ability to failover to connected clients demonstrates that the primary service layer remains operational, but the disruption to load balancing functionality could lead to uneven distribution of client requests across available resources, potentially causing performance degradation or resource exhaustion on remaining active servers. This partial service disruption creates a scenario where attackers can cause availability issues while maintaining access to the system.
The impact extends beyond simple denial-of-service conditions as the vulnerability affects the fundamental reliability of the load balancing infrastructure that many enterprise networks depend upon for maintaining service availability and optimal resource utilization. Organizations implementing Secure Access servers with load balancing capabilities face potential business disruption risks, particularly in environments where consistent service delivery and balanced resource allocation are critical for operational continuity. The vulnerability's persistence even after crash recovery indicates that the underlying code structure lacks proper error handling mechanisms to prevent cascading failures.
Mitigation strategies should include immediate deployment of the vendor-provided security patch for version 14.57 or later, which addresses the null pointer dereference condition through proper input validation and defensive programming practices. Network-level protections such as implementing firewall rules to restrict access to load balancing ports from untrusted networks can provide temporary mitigation while patches are deployed. Additionally, monitoring systems should be configured to detect unusual patterns of load balancer crashes or service disruptions that could indicate exploitation attempts. Organizations should also consider implementing intrusion detection systems capable of identifying the specific packet patterns associated with this vulnerability, enabling proactive threat hunting and incident response capabilities.
The vulnerability demonstrates how seemingly minor coding errors in critical system components can create significant operational risks, aligning with ATT&CK technique T1499.004 for network disruption attacks. Security teams should conduct comprehensive vulnerability assessments of all Secure Access server deployments to identify affected systems and prioritize remediation efforts based on risk exposure levels and business criticality of the services protected by these load balancing configurations.