Laravel Reverb is a real-time WebSocket backend for Laravel applications that uses Redis channels to pass messages. In versions 1.6.3 and below, Reverb directly passes data received from Redis into PHP's unserialize() function without restricting which classes can be instantiated. This unsafe deserialization (CWE-502) allows attackers to craft malicious payloads that, when deserialized, can trigger remote code execution (RCE) on the server. The vulnerability is particularly dangerous because Redis servers are frequently deployed without authentication, allowing attackers to publish malicious payloads to Redis channels. However, the vulnerability only manifests when horizontal scaling is enabled (REVERB_SCALING_ENABLED=true), as this triggers the vulnerable deserialization logic. The flaw was fixed in version 1.7.0 by presumably adding class restrictions or safer deserialization methods. The CVSS 3.1 score of 9.8 indicates a critical severity with network attack vector, no privileges or user interaction required, and full impact on confidentiality, integrity, and availability. No known exploits are currently reported in the wild, but the ease of exploitation and common Redis misconfigurations make this a high-risk issue. Workarounds include enforcing strong Redis authentication, limiting Redis access to private networks or localhost, or disabling horizontal scaling to avoid the vulnerable code path.

For European organizations, this vulnerability poses a severe risk of remote code execution leading to full system compromise, data breaches, service disruption, and lateral movement within networks. Organizations using Laravel Reverb in horizontally scaled environments with Redis instances exposed or weakly secured are particularly vulnerable. Exploitation could lead to theft of sensitive data, deployment of ransomware or malware, and disruption of critical web services. Given the popularity of Laravel in Europe’s web development ecosystem and the common use of Redis for caching and messaging, many organizations could be affected. The impact extends to cloud-hosted environments where Redis instances might be misconfigured or accessible over public or shared networks. The critical severity and ease of exploitation without authentication make this a top priority for incident prevention and response.

1. Immediately upgrade Laravel Reverb to version 1.7.0 or later to apply the official fix. 2. If upgrading is not immediately possible, disable horizontal scaling by setting REVERB_SCALING_ENABLED=false to bypass the vulnerable deserialization logic. 3. Enforce strong authentication on Redis servers by setting robust passwords and enabling Redis AUTH. 4. Restrict Redis network access to trusted hosts only, preferably limiting it to localhost or private network segments using firewall rules or network ACLs. 5. Monitor Redis logs and network traffic for suspicious publish commands or unexpected connections. 6. Conduct code audits to ensure no other unsafe unserialize() calls exist in the application stack. 7. Implement application-layer input validation and consider using safer serialization formats like JSON instead of PHP serialization. 8. Regularly scan and audit infrastructure for exposed Redis instances and remediate any found. 9. Educate development and operations teams about the risks of unsafe deserialization and secure Redis deployment best practices.