Ubuntu Security Notice 3653-1 - Jann Horn and Ken Johnson discovered that microprocessors utilizing speculative execution of a memory read may allow unauthorized memory reads via a sidechannel attack. This flaw is known as Spectre Variant 4. A local attacker could use this to expose sensitive information, including kernel memory. It was discovered that the netlink subsystem in the Linux kernel did not properly restrict observations of netlink messages to the appropriate net namespace. A local attacker could use this to expose sensitive information. Various other issues were also addressed.
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