CVE-2021-21309

An integer overflow was found in Redis. Redis 4.0 or newer uses a configurable limit for the maximum supported bulk input size. The default size is 512MB which is a safe value for all platforms. Authenticated Redis users could increase the bulk input size by changing the “proto-max-bulk-len” configuration parameter, leading to heap corruption and potentially remote code execution.

Mitigation

As recommended in the upstream advisory, this issue can be mitigated by preventing clients from directly executing CONFIG SET:

• Using Redis 6.0 or newer, ACL configuration can be used to block the command.
• Using older versions, the rename-command configuration directive can be used to rename the command to a random string unknown to users, rendering it inaccessible.