A severe security flaw has been found in Redis servers that could allow an attacker to take full control of a system. This vulnerability, tracked as CVE-2025-49844, is a use-after-free error within the Lua scripting engine, a core component used by many Redis deployments. An authenticated user with permission to run Lua scripts can exploit this flaw by tricking the server’s memory management system. This grants them the ability to run their own code remotely, making it a critical threat to data integrity and network security.
The vulnerability stems from a fundamental issue in how Redis manages memory when running Lua scripts. By crafting a specially designed script, an attacker can manipulate the garbage collector, a process that automatically reclaims memory no longer in use. This manipulation causes the system to improperly handle memory, leading to a use-after-free condition. In this state, the program tries to access a block of memory that has already been deallocated, which can corrupt the system’s execution flow.
An attacker can leverage this memory corruption to bypass security controls and inject their own malicious code into the server’s process. Gaining the ability to execute arbitrary code provides an attacker with complete control over the Redis instance. This level of access means they could steal, alter, or delete any data stored in the database. The potential for such a devastating attack highlights the severity of this flaw and the urgent need for a fix.
The consequences of a successful exploit are dire. Not only can attackers compromise the confidentiality and integrity of the data within the database, but they can also cause a denial-of-service, making the system unavailable. Moreover, a compromised Redis server can serve as a stepping stone for an attacker to move deeper into a company’s network. From this foothold, they could attempt to escalate their privileges and attack other systems, creating a chain reaction of compromises.
This vulnerability is particularly concerning due to its widespread impact. The Lua scripting engine has been a key feature of Redis for many years, meaning that all versions that use it are at risk. This includes a vast number of deployments across various industries, from web applications to financial services. The widespread nature of this flaw necessitates immediate action from administrators and developers to patch their systems and mitigate the risk.
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