Synopsis
The remote Ubuntu host is missing a security-related patch.
Description
Karthikeyan Bhargavan discovered that NSS incorrectly handled state transitions for the TLS state machine. If a remote attacker were able to perform a man-in-the-middle attack, this flaw could be exploited to skip the ServerKeyExchange message and remove the forward-secrecy property. (CVE-2015-2721)
Bob Clary, Christian Holler, Bobby Holley, and Andrew McCreight discovered multiple memory safety issues in Thunderbird. If a user were tricked in to opening a specially crafted website in a browsing context, an attacker could potentially exploit these to cause a denial of service via application crash, or execute arbitrary code with the privileges of the user invoking Thunderbird. (CVE-2015-2724)
Ronald Crane discovered multiple security vulnerabilities. If a user were tricked in to opening a specially crafted website in a browsing context, an attacker could potentially exploit these to cause a denial of service via application crash, or execute arbitrary code with the privileges of the user invoking Thunderbird. (CVE-2015-2734, CVE-2015-2735, CVE-2015-2736, CVE-2015-2737, CVE-2015-2738, CVE-2015-2739, CVE-2015-2740)
Matthew Green discovered a DHE key processing issue in NSS where a MITM could force a server to downgrade TLS connections to 512-bit export-grade cryptography. An attacker could potentially exploit this to impersonate the server. (CVE-2015-4000).
Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
Solution
Update the affected thunderbird package.