CVE-2025-21605

A flaw was found in the Redis server. This flaw allows an unauthenticated client to cause an unlimited growth of output buffers until the server runs out of memory or is killed. By default, the Redis configuration does not limit the output buffer of normal clients (see client-output-buffer-limit). Therefore, the output buffer can grow unlimitedly over time. As a result, the service is exhausted, and the memory is unavailable.

When password authentication is enabled on the Redis server but no password is provided, the client can still cause the output buffer to grow from "NOAUTH" responses until the system runs out of memory.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

A workaround to mitigate this problem without patching the redis-server executable is to block access to prevent unauthenticated users from connecting to Redis. This can be done in the following different ways:

• Using network access control tools like firewalls, iptables, security groups, etc.
• Enabling TLS and requiring users to authenticate using client side certificates.