HAProxyMessageDecoder Stack Exhaustion DoS

Impact

A StackOverflowError can be raised when parsing a malformed crafted message due to an infinite recursion.

Patches

Users should upgrade to 4.1.86.Final.

Workarounds

There is no workaround, except using a custom HaProxyMessageDecoder.

References

When parsing a TLV with type = PP2_TYPE_SSL, the value can be again a TLV with type = PP2_TYPE_SSL and so on.
The only limitation of the recursion is that the TLV length cannot be bigger than 0xffff because it is encoded in an unsigned short type.
Providing a TLV with a nesting level that is large enough will lead to raising of a StackOverflowError.
The StackOverflowError will be caught if HAProxyMessageDecoder is used as part of Netty’s ChannelPipeline, but using it directly without the ChannelPipeline will lead to a thrown exception / crash.

For more information

If you have any questions or comments about this advisory:

• Open an issue in netty