A flaw was found in Netty's `RedisArrayAggregator` component. A remote attacker can exploit this vulnerability by sending specially crafted nested Redis (RESP) array headers. This can cause the `RedisArrayAggregator` to eagerly preallocate a large amount of heap memory, leading to heap memory exhaustion and a Denial of Service (DoS) for applications using `RedisDecoder` with `RedisArrayAggregator` on untrusted traffic.

## Summary

`RedisArrayAggregator` recently added `maxElements` and `maxNestedArrayDepth` limits to fix public Redis resource-exhaustion advisories. The limits are independent, but the allocator remains eager: every positive nested RESP array header creates `new ArrayList<RedisMessage>(length)` before any child element exists.

With the default constructor, an attacker can send nested array headers with length `1,000,000` until the default nesting limit of `1024` is reached. This can reserve up to `1,024,000,000` child slots from roughly 12 KB of RESP input. This is backing capacity, not logical list size: `ArrayList(int)` constructs an empty list with the specified initial capacity.

## Technical Details

Current `decodeRedisArrayHeader(...)` checks the two limits independently:

```java if (header.length() > maxElements) { throw new CodecException("this codec doesn't support longer length than " + maxElements); }

if (depths.size() >= maxNestedArrayDepth) { releaseAndClearDepths(); throw new CodecException("max nested array depth exceeded: " + maxNestedArrayDepth); } depths.push(new AggregateState((int) header.length())); ```

`AggregateState` i

netty-4.1.138-1.1 on GA media

Affected: Ubuntu:Pro:14.04:LTS: netty, Ubuntu:Pro:16.04:LTS: netty, Ubuntu:Pro:18.04:LTS: netty, Ubuntu:Pro:20.04:LTS: netty, Ubuntu:Pro:22.04:LTS: netty, Ubuntu:Pro:24.04:LTS: netty, Ubuntu:Pro:26.04:LTS: netty

A flaw was found in Netty's `RedisArrayAggregator` component. A remote attacker can exploit this vulnerability by sending specially crafted nested Redis (RESP) array headers. This can cause the `RedisArrayAggregator` to eagerly preallocate a large amount of heap memory, leading to heap memory exhaustion and a Denial of Service (DoS) for applications using `RedisDecoder` with `RedisArrayAggregator` on untrusted traffic.