CVE-2025-14769 in FreeBSD
Summary
by MITRE • 03/09/2026
In some cases, the `tcp-setmss` handler may free the packet data and throw an error without halting the rule processing engine. A subsequent rule can then allow the traffic after the packet data is gone, resulting in a NULL pointer dereference.
Maliciously crafted packets sent from a remote host may result in a Denial of Service (DoS) if the `tcp-setmss` directive is used and a subsequent rule would allow the traffic to pass.
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Analysis
by VulDB Data Team • 03/17/2026
The vulnerability identified as CVE-2025-14769 represents a critical flaw in packet processing mechanisms within network security frameworks that utilize tcp-setmss directives. This issue manifests when the system encounters packets that trigger the tcp-setmss handler, which is designed to modify the Maximum Segment Size parameter in TCP packets during network traffic processing. The flaw occurs specifically during the handling of malformed or specially crafted packets that exploit the interaction between the tcp-setmss processing logic and subsequent rule evaluation.
The technical implementation of this vulnerability stems from improper error handling within the packet processing engine. When the tcp-setmss handler processes certain packets, it may prematurely free the packet data structures while simultaneously throwing an error condition. This premature memory deallocation creates a scenario where the rule processing engine continues execution despite the error state, leading to inconsistent packet handling behavior. The fundamental issue lies in the lack of proper state management and error propagation mechanisms that should prevent further processing of already-destroyed packet data.
From an operational perspective, this vulnerability creates a significant denial of service risk for systems implementing tcp-setmss directives in their network filtering configurations. The attack vector requires a remote malicious actor to craft specific packets that trigger the vulnerable code path, but the impact can be severe as it allows for system instability and potential service disruption. The NULL pointer dereference that occurs when subsequent rules attempt to process the freed packet data can result in kernel crashes, application termination, or complete system unresponsiveness depending on the implementation details.
The vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and specifically relates to the broader category of improper error handling in network processing systems. From an ATT&CK framework perspective, this represents a privilege escalation and denial of service technique that could be leveraged by threat actors to disrupt network services. The vulnerability demonstrates poor defensive programming practices where error conditions are not properly propagated through the system state, allowing execution to continue in an inconsistent state.
Mitigation strategies should focus on implementing proper error handling protocols within the tcp-setmss processing logic to ensure that when packet data is freed, the rule processing engine terminates execution rather than continuing with potentially invalid state. Network administrators should consider disabling tcp-setmss directives if they are not actively required, or implement additional packet validation mechanisms to filter out maliciously crafted traffic before it reaches the vulnerable processing path. Regular security updates and patches should be applied immediately to address this vulnerability, and network monitoring should be enhanced to detect unusual packet processing patterns that may indicate exploitation attempts.