CVE-2026-77549 in Cloud Gateways
Summary
by MITRE • 08/26/2026
A malicious actor with access to the network and under certain conditions could exploit an Improper Neutralization of CRLF Sequences vulnerability found in certain devices running UniFi OS to bypass authentication to such UniFi OS devices or instances.
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Analysis
by VulDB Data Team • 08/26/2026
The identified vulnerability represents a critical security flaw within the UniFi OS platform, specifically categorized as Improper Neutralization of Carriage Return and Line Feed sequences, commonly known as CRLF injection. This type of vulnerability arises when an application processes user-supplied input without adequately validating or sanitizing special characters that control message formatting in protocols such as HTTP. In this specific instance, the flaw allows a malicious actor who has established access to the network infrastructure to manipulate request headers or parameters by injecting newline characters. These injected sequences can alter how the server interprets subsequent parts of an HTTP request, potentially allowing the attacker to inject additional header fields or even modify response content. The core technical failure lies in the application's inability to properly neutralize these control characters before they are processed by the underlying web server or framework components responsible for handling authentication logic and session management.
From a technical perspective, CRLF injection vulnerabilities often lead to more severe secondary attacks such as HTTP Response Splitting or Cross-Site Scripting (XSS). However, in this context, the exploitation path is directed specifically toward bypassing authentication mechanisms. By carefully crafting requests that exploit the parsing ambiguity introduced by the injected line breaks, an attacker can trick the UniFi OS device into accepting unauthorized credentials or skipping legitimate verification steps entirely. This effectively grants the adversary access to administrative interfaces and system controls without possessing valid login information. The vulnerability is particularly dangerous because it requires only network-level access rather than physical proximity or prior compromise of user accounts, making it a significant risk for organizations that rely on UniFi OS for centralized network management and security monitoring.
The operational impact of this authentication bypass is severe, as UniFi OS devices typically serve as the central control plane for enterprise Wi-Fi networks, switches, and gateways. Unauthorized access to these systems allows an attacker to reconfigure network settings, isolate critical infrastructure from management planes, exfiltrate sensitive configuration data containing credentials or encryption keys, and potentially pivot into other segments of the corporate network. Furthermore, since UniFi OS often integrates with broader security ecosystems, compromising it could undermine visibility and control over endpoint protection policies and intrusion detection systems. The ability to bypass authentication means that traditional perimeter defenses such as firewalls may be insufficient if internal threats are present or if an attacker gains foothold through other vectors like phishing or compromised endpoints within the same broadcast domain.
To mitigate this risk, immediate action is required to apply vendor-provided patches that address the input validation logic for CRLF characters in affected versions of UniFi OS. Administrators should ensure that all management interfaces are updated to the latest stable release where these sanitization routines have been hardened. In addition to patching, network segmentation strategies should be reviewed to restrict access to UniFi controllers from untrusted or public networks, ensuring they are only accessible via secure, authenticated channels such as VPNs with strong multi-factor authentication enabled for administrative accounts. Security teams should also monitor logs for anomalous HTTP request patterns indicative of CRLF injection attempts and consider deploying Web Application Firewalls configured to detect and block malformed headers containing control characters. This vulnerability is classified under CWE-74 Improper Neutralization Special Elements in Output Used by a Downstream Component, reflecting the failure to sanitize special elements that could alter command structure or data interpretation. From an offensive security framework perspective, this exploitation technique aligns with ATT&CK techniques related to Initial Access and Privilege Escalation via protocol manipulation, highlighting the need for robust input validation across all web-facing components of network management platforms.