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The vulnerability operates within Laravel Reverb’s horizontal scaling feature, which is activated by setting REVERB_SCALING_ENABLED=true. When enabled, multiple Reverb instances communicate through Redis PubSub channels to synchronize data across servers. The security flaw exists in the data handling process from these channels. Specifically, the application receives messages from Redis and passes the raw string data directly into PHP’s unserialize() function without any filtering or validation. PHP’s unserialize function can instantiate objects of any class that is available in the application’s scope, including potentially hazardous classes. Attackers can exploit this by gaining access to the Redis server, which is frequently deployed without authentication, as noted in common practices. By crafting a malicious serialized payload and publishing it to the appropriate Redis PubSub channel, an attacker can inject arbitrary objects into the Reverb server’s execution flow. When the Reverb server processes this payload, the unserialize function creates objects from the attacker-controlled data, triggering methods like __wakeup() or __destruct() that can execute code. This object injection leads to remote code execution, allowing the attacker to run arbitrary commands on the server. The vulnerability is particularly dangerous because Redis servers often lack password protection, making them easily accessible on internal networks. The attack requires horizontal scaling to be active, as the vulnerable code path is only used in that configuration. Versions prior to v1.7.0 are affected because they lack proper class restrictions during deserialization. The fix in v1.7.0 involves validating or sanitizing input before unserialization, preventing instantiation of unauthorized classes. This issue highlights the risks of insecure deserialization in distributed systems relying on message queues like Redis.
Platform: Laravel Reverb
Version: prior to v1.7.0
Vulnerability: Remote Code Execution
Severity: Critical
date: Unknown
Prediction: Patched in v1.7.0
What Undercode Say:
Analytics:
- Check Redis authentication: `redis-cli AUTH password`
– Set Redis password: `redis-cli CONFIG SET requirepass strongpassword`
– Disable scaling: `export REVERB_SCALING_ENABLED=false`
– Verify Reverb version: `composer show laravel/reverb`
how Exploit:
Attacker publishes malicious serialized data to Redis PubSub channel when horizontal scaling enabled and Redis unauthenticated, leading to arbitrary object instantiation and code execution via unserialize().
Protection from this CVE
Update to Laravel Reverb v1.7.0. Enable Redis authentication with strong password. Disable horizontal scaling if unused via REVERB_SCALING_ENABLED=false.
Impact:
Remote Code Execution enabling full server compromise. Affects systems with horizontal scaling enabled and Redis without authentication. Leads to data theft, service disruption.
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Sources:
Reported By: github.com
Extra Source Hub:
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