Multiple integer overflows in the (1) PL_Base64Decode and (2) PL_Base64Encode functions in nsprpub/lib/libc/src/base64.c in Mozilla Firefox before 3.0.12, Thunderbird before 2.0.0.24, and SeaMonkey before 1.1.19 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via unspecified vectors that trigger buffer overflows.