Ubuntu Security Notice 3999-1 - Eyal Ronen, Kenneth G. Paterson, and Adi Shamir discovered that GnuTLS was vulnerable to a timing side-channel attack known as the "Lucky Thirteen" issue. A remote attacker could possibly use this issue to perform plaintext-recovery attacks via analysis of timing data. This issue only affected Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. Tavis Ormandy discovered that GnuTLS incorrectly handled memory when verifying certain X.509 certificates. 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 18.04 LTS, Ubuntu 18.10, and Ubuntu 19.04. Various other issues were also addressed.
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