Redis Warns of Critical Flaw Impacting Thousands of Instances

An anonymous reader quotes a report from BleepingComputer: The Redis security team has released patches for a maximum severity vulnerability that could allow attackers to gain remote code execution on thousands of vulnerable instances. Redis (short for Remote Dictionary Server) is an open-source data structure store used in approximately 75% of cloud environments, functioning like a database, cache, and message broker, and storing data in RAM for ultra-fast access. The security flaw (tracked as CVE-2025-49844) is caused by a 13-year-old use-after-free weakness found in the Redis source code and can be exploited by authenticated threat actors using a specially crafted Lua script (a feature enabled by default). Successful exploitation enables them to escape the Lua sandbox, trigger a use-after-free, establish a reverse shell for persistent access, and achieve remote code execution on the targeted Redis hosts.

After compromising a Redis host, attackers can steal credentials, deploy malware or cryptocurrency mining tools, extract sensitive data from Redis, move laterally to other systems within the victim's network, or use stolen information to gain access to other cloud services. 'This grants an attacker full access to the host system, enabling them to exfiltrate, wipe, or encrypt sensitive data, hijack resources, and facilitate lateral movement within cloud environments,' said Wiz researchers, who reported the security issue at Pwn2Own Berlin in May 2025 and dubbed it RediShell.

While successful exploitation requires attackers first to gain authenticated access to a Redis instance, Wiz found around 330,000 Redis instances exposed online, with at least 60,000 of them not requiring authentication. Redis and Wiz urged admins to patch their instances immediately by applying security updates released on Friday, 'prioritizing those that are exposed to the internet.' To further secure their Redis instances against remote attacks, admins can also enable authentication, disable Lua scripting and other unnecessary commands, launch Redis using a non-root user account, enable Redis logging and monitoring, limit access to authorized networks only, and implement network-level access controls using firewalls and Virtual Private Clouds (VPCs).

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