CVE-2026-77544 in Cloud Gateways
Summary
by MITRE • 09/22/2026
A malicious actor with access to the network could exploit an Out-of-bounds Write vulnerability found in certain UniFi gateway devices to execute a Denial of Service (DoS) attack on the device.
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Analysis
by VulDB Data Team • 09/22/2026
The identified security flaw represents a critical memory management error within the firmware architecture of specific Ubiquiti UniFi gateway appliances, classified technically as an Out-of-bounds Write vulnerability. This type of defect occurs when software writes data to a memory location that falls outside the intended buffer boundaries, potentially overwriting adjacent memory structures such as control flow metadata or other variables essential for system stability. In the context of network infrastructure devices like gateways and routers, which often run complex embedded operating systems with limited resource constraints, such memory corruption is particularly dangerous because it can disrupt the normal execution flow without necessarily providing code execution capabilities to an attacker immediately. The vulnerability stems from insufficient boundary checks during packet processing or configuration handling routines, allowing a malicious actor who has gained access to the local network segment to craft specific malformed inputs that trigger this erroneous write operation.
From an operational perspective, the primary impact of exploiting this Out-of-bounds Write is a Denial of Service condition affecting the targeted UniFi device. By triggering memory corruption through crafted network traffic or administrative requests, an attacker can cause the gateway process to crash, hang, or enter an unrecoverable error state. This results in the loss of connectivity for all devices relying on that specific gateway for internet access and local network segmentation. Unlike vulnerabilities that allow remote code execution which might be used for data exfiltration or lateral movement within a corporate environment, this particular flaw is leveraged specifically to disrupt availability. The attacker does not need elevated privileges beyond basic network reachability; simply being present on the same broadcast domain as the vulnerable device provides sufficient access vectors to send the malicious payloads required to trigger the fault.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-787, which defines out-of-bounds write errors that can lead to arbitrary code execution or system crashes depending on what memory regions are overwritten. Furthermore, in terms of tactical classification under the MITRE ATT&CK framework, this exploitation technique falls under T1499 Endpoint Denial of Service, specifically involving resource exhaustion via software vulnerabilities rather than simple volume-based attacks. The ability to crash a network gateway from within the local network highlights significant gaps in input validation and memory safety practices within the affected firmware versions. Such flaws are often exacerbated by the use of lower-level languages like C or C++ where manual memory management is required, increasing the risk of buffer overflow conditions if developers fail to implement rigorous bounds checking mechanisms before writing data to allocated buffers.
Mitigation strategies for this vulnerability must focus on both immediate remediation and long-term architectural improvements. The most effective countermeasure is to apply the latest firmware updates provided by Ubiquiti Systems, which typically include patches that enforce strict boundary checks and validate input lengths prior to memory allocation or write operations. Organizations should prioritize patching these gateway devices as part of their routine maintenance cycles, ensuring that all network infrastructure components are running supported versions with known security fixes in place. Additionally, implementing network segmentation can help limit the blast radius if a vulnerability is exploited; by placing critical gateways behind firewalls or restricting administrative access to trusted management VLANs only, administrators reduce the attack surface available to potential adversaries who might otherwise gain foothold on less secure parts of the internal network. Regular security audits and penetration testing focused on embedded devices can also help identify similar memory safety issues before they are exploited in production environments.