Ubuntu Security Notice 4966-2 - USN-4966-1 fixed a vulnerability in libx11. This update provides the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM. It was discovered that libx11 incorrectly validated certain parameter lengths. A remote attacker could possibly use this issue to trick libx11 into emitting extra X protocol requests. Various other issues were also addressed.
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