CVE-2006-6505: Undefined Security Weakness

Multiple heap-based buffer overflows in Mozilla Thunderbird before 1.5.0.9 and SeaMonkey before 1.0.7 allow remote attackers to execute arbitrary code via 1 external message modies with long Content-Type headers or 2 long RFC2047-encoded MIME non-ASCII headers...

Mail header processing heap overflows — Mozilla

Georgi Guninski reported that long Content-Type headers in external message bodies could cause a heap buffer overflow when processing mail headers. While working on that code David Bienvenu discovered a similar overflow could occur when processing long rfc2047-encoded headers...