Several security issues were fixed in Thunderbird.
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)
20 July 2015
A security issue affects these releases of Ubuntu and its derivatives:
Several security issues were fixed in Thunderbird.
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)
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
After a standard system update you need to restart Thunderbird to make all the necessary changes.
Vulmon