CVE-2005-0039

Certain configurations of IPsec, when using Encapsulating Security Payload
(ESP) in tunnel mode, integrity protection at a higher layer, or
Authentication Header (AH), allow remote attackers to decrypt IPSec
communications by modifying the outer packet in ways that cause plaintext
data from the inner packet to be returned in ICMP messages, as demonstrated
using bit-flipping attacks and (1) Destination Address Rewriting, (2) a
modified header length that causes portions of the packet to be interpreted
as IP Options, or (3) a modified protocol field and source address.