CVE-2021-21309

Redis is an open-source, in-memory database that persists on disk. In
affected versions of Redis an integer overflow bug in 32-bit Redis version
4.0 or newer could be exploited to corrupt the heap and potentially result
with remote code execution. Redis 4.0 or newer uses a configurable limit
for the maximum supported bulk input size. By default, it is 512MB which is
a safe value for all platforms. If the limit is significantly increased,
receiving a large request from a client may trigger several integer
overflow scenarios, which would result with buffer overflow and heap
corruption. We believe this could in certain conditions be exploited for
remote code execution. By default, authenticated Redis users have access to
all configuration parameters and can therefore use the “CONFIG SET
proto-max-bulk-len” to change the safe default, making the system
vulnerable. This problem only affects 32-bit Redis (on a 32-bit system,
or as a 32-bit executable running on a 64-bit system). The problem is
fixed in version 6.2, and the fix is back ported to 6.0.11 and 5.0.11. Make
sure you use one of these versions if you are running 32-bit Redis. An
additional workaround to mitigate the problem without patching the
redis-server executable is to prevent 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. Please note that this workaround may have
an additional impact on users or operational systems that expect CONFIG SET to behave in certain ways.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=983446&gt;