The gnutls_ocsp_resp_check_crt function in lib/x509/ocsp.c in GnuTLS before 3.4.15 and 3.5.x before 3.5.4 does not verify the serial length of an OCSP response, which might allow remote attackers to bypass an intended certificate validation mechanism via vectors involving trailing bytes left by gnutls_malloc.

Affected: Ubuntu:14.04:LTS: gnutls26, Ubuntu:16.04:LTS: gnutls28

Stefan Buehler discovered that GnuTLS incorrectly verified the serial length of OCSP responses. A remote attacker could possibly use this issue to bypass certain certificate validation measures. This issue only applied to Ubuntu 16.04 LTS. (CVE-2016-7444)

Shi Lei discovered that GnuTLS incorrectly handled certain warning alerts. A remote attacker could possibly use this issue to cause GnuTLS to hang, resulting in a denial of service. This issue has only been addressed in Ubuntu 16.04 LTS and Ubuntu 16.10. (CVE-2016-8610)

It was discovered that GnuTLS incorrectly decoded X.509 certificates with a Proxy Certificate Information extension. A remote attacker could use this issue to cause GnuTLS to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 16.04 LTS and Ubuntu 16.10. (CVE-2017-5334)

It was discovered that GnuTLS incorrectly handled certain OpenPGP certificates. A remote attacker could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2017-5335, CVE-2017-5336, CVE-2017-5337)