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Unauthenticated Users Can Crash Redis with Malicious Requests

published 2 years ago

Summary

An attacker can crash the Redis database server by sending specially crafted requests, potentially causing downtime. This vulnerability affects unpatched versions of Redis, but patching to the latest version (6.2.6, 6.0.16, or 5.0.14) or blocking unauthenticated users from accessing the server can prevent the issue. For now, consider restricting access to authenticated users only.

What to do

Update redis to version 6.2.6.

Affected software

Ecosystem	Vendor	Product	Affected versions
Bitnami	–	redis	>= 6.2.0, < 6.2.6 Fix: upgrade to 6.2.6

Original advisory text

DoS vulnerability in Redis

Redis is an open source, in-memory database that persists on disk. When parsing an incoming Redis Standard Protocol (RESP) request, Redis allocates memory according to user-specified values which determine the number of elements (in the multi-bulk header) and size of each element (in the bulk header). An attacker delivering specially crafted requests over multiple connections can cause the server to allocate significant amount of memory. Because the same parsing mechanism is used to handle authentication requests, this vulnerability can also be exploited by unauthenticated users. The problem is fixed in Redis versions 6.2.6, 6.0.16 and 5.0.14. An additional 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 different ways: Using network access control tools like firewalls, iptables, security groups, etc. or Enabling TLS and requiring users to authenticate using client side certificates.

References

Timeline

Published6 Mar 2024

Updated13 Mar 2026

First seen13 Mar 2026

Sources

BIT-redis-2021-32675 · OSV

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