CVE-2026-23524 in reverb
Summary
by MITRE • 01/22/2026
Laravel Reverb provides a real-time WebSocket communication backend for Laravel applications. In versions 1.6.3 and below, Reverb passes data from the Redis channel directly into PHP’s unserialize() function without restricting which classes can be instantiated, which leaves users vulnerable to Remote Code Execution. The exploitability of this vulnerability is increased because Redis servers are commonly deployed without authentication, but only affects Laravel Reverb when horizontal scaling is enabled (REVERB_SCALING_ENABLED=true). This issue has been fixed in version 1.7.0. As a workaround, require a strong password for Redis access and ensure the service is only accessible via a private network or local loopback, and/or set REVERB_SCALING_ENABLED=false to bypass the vulnerable logic entirely (if the environment uses only one Reverb node).
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Analysis
by VulDB Data Team • 01/22/2026
Laravel Reverb represents a real-time WebSocket communication backend designed for Laravel applications, facilitating bidirectional communication between servers and clients through WebSocket protocols. The vulnerability identified as CVE-2026-23524 specifically targets versions 1.6.3 and earlier, where the system exhibits a critical flaw in its data handling mechanisms. This vulnerability stems from the improper sanitization of data retrieved from Redis channels, creating an avenue for remote code execution attacks that could compromise entire application environments.
The technical flaw manifests when Reverb processes data from Redis channels and directly feeds this information into PHP's unserialize() function without implementing class restriction mechanisms. This behavior creates a deserialization vulnerability that aligns with CWE-502, which categorizes insecure deserialization as a critical security weakness. When an attacker can control the data passed to unserialize(), they can craft malicious payloads that instantiate arbitrary PHP classes, potentially leading to remote code execution. The vulnerability is particularly dangerous because Redis servers are frequently deployed without authentication mechanisms, making them easily accessible to attackers who can manipulate the data flowing through these channels.
The operational impact of this vulnerability is significant, as it enables attackers to execute arbitrary code on systems running affected versions of Laravel Reverb. This remote code execution capability allows adversaries to gain full control over the affected servers, potentially leading to data breaches, system compromise, and further lateral movement within network environments. The vulnerability specifically requires horizontal scaling to be enabled through the REVERB_SCALING_ENABLED=true environment variable, which means it only affects deployments using multiple Reverb nodes. This constraint reduces the overall attack surface but does not eliminate the risk entirely, as organizations with scaled deployments remain highly vulnerable.
The exploitation of this vulnerability follows established patterns documented in various attack frameworks including ATT&CK's T1059.007 for remote code execution via deserialization attacks. Attackers typically craft malicious serialized objects that, when processed by the vulnerable unserialize() call, trigger the execution of malicious PHP code. This process often involves leveraging existing PHP classes or creating new ones that can be used to establish reverse shells, download additional malware, or perform other malicious activities. The attack vector is particularly concerning because it can be executed remotely without authentication, provided the attacker has access to the Redis server or can intercept data flowing through it.
Organizations can mitigate this vulnerability through several approaches that align with security best practices and industry standards. The primary solution involves upgrading to Laravel Reverb version 1.7.0 or later, which implements proper class restriction mechanisms in the deserialization process. Additionally, implementing strong Redis authentication through password protection creates a critical barrier that prevents unauthorized access to the Redis data stores. Network segmentation practices should ensure that Redis services are only accessible through private networks or local loopback interfaces, preventing external exploitation attempts. The most definitive workaround involves setting REVERB_SCALING_ENABLED=false to completely bypass the vulnerable code path, though this approach may impact scalability requirements for distributed deployments. These mitigations collectively address the vulnerability while maintaining operational functionality and align with established security frameworks for protecting against deserialization attacks.