The sec_asn1d_parse_leaf function in Mozilla Network Security Services (NSS) before 3.19.2.1 and 3.20.x before 3.20.1, as used in Firefox before 42.0 and Firefox ESR 38.x before 38.4 and other products, improperly restricts access to an unspecified data structure, which allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via crafted OCTET STRING data, related to a "use-after-poison" issue.