CVE-2026-19314 in Fireware
Summary
by MITRE • 08/28/2026
An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.
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Analysis
by VulDB Data Team • 08/28/2026
The identified security flaw resides within the Internet Key Exchange daemon, commonly referred to as iked, which is a critical component of the WatchGuard Fireware operating system responsible for managing IPsec tunnel negotiations and key exchanges. This specific vulnerability stems from an integer underflow condition that occurs during the processing of incoming network packets destined for VPN establishment or maintenance. The root cause lies in inadequate validation of numerical values associated with packet headers or payload structures, allowing a remote attacker to supply input data where arithmetic operations result in negative numbers being interpreted as large positive unsigned integers due to standard two's complement representation rules. This mathematical error disrupts the internal state machine logic within the iked process, leading to unexpected behavior when allocating memory buffers or calculating sequence numbers for encrypted traffic streams.
From an operational perspective, this vulnerability enables a remote unauthenticated attacker to trigger a Denial of Service condition without requiring any prior authentication credentials. By sending specially crafted network packets that exploit the integer underflow, the attacker can cause the iked process to crash, hang, or enter an unrecoverable error state. Since the Internet Key Exchange daemon is essential for establishing and maintaining secure VPN tunnels, its failure effectively halts all IPsec-based communications passing through the affected firewall device. This results in a complete loss of connectivity for users relying on site-to-site or remote access VPNs, impacting business continuity and potentially exposing internal networks if failover mechanisms are not properly configured to handle such service disruptions. The ability to exploit this flaw remotely without authentication significantly lowers the barrier to entry for malicious actors seeking to disrupt organizational network infrastructure.
In terms of industry classification standards, this vulnerability aligns with CWE-191, which defines integer underflow as a weakness where an arithmetic operation results in a value that is smaller than what can be represented by the target data type. This often leads to buffer overflows or logic errors depending on how the resulting incorrect value is utilized within the application flow. Furthermore, from a tactical standpoint relevant to threat intelligence frameworks like MITRE ATT&CK, this exploitation technique falls under the category of Denial of Service, specifically targeting service availability by exhausting system resources or crashing critical services. The attack vector is classified as Network-based and requires no user interaction, making it particularly dangerous for devices exposed directly to untrusted networks such as the public internet.
To mitigate the risks associated with this vulnerability, organizations utilizing WatchGuard Fireware appliances must ensure that their firmware versions are updated to include patches specifically addressing the integer underflow in the iked process. It is imperative to consult official vendor advisories and release notes for precise version requirements and patching instructions. In environments where immediate patching is not feasible due to operational constraints, network segmentation strategies should be employed to restrict access to management interfaces and VPN endpoints from untrusted networks until the vulnerability is remediated. Additionally, implementing strict ingress filtering rules can help block malformed packets that exhibit characteristics of this exploit attempt, although such measures are considered compensatory controls rather than definitive fixes. Regular monitoring of system logs for anomalies in IKE negotiation failures or unexpected daemon restarts can also aid in early detection and response to potential exploitation attempts.