The ASN.1 decoder in the QuickDER decoder in Mozilla Network Security Services (NSS) before 3.13.4, as used in Firefox 4.x through 12.0, Firefox ESR 10.x before 10.0.5, Thunderbird 5.0 through 12.0, Thunderbird ESR 10.x before 10.0.5, and SeaMonkey before 2.10, allows remote attackers to cause a denial of service (application crash) via a zero-length item, as demonstrated by (1) a zero-length basic constraint or (2) a zero-length field in an OCSP response.