Researchers from universities in Germany and Israel have disclosed the details of a new timing attack that could allow malicious actors to decrypt TLS-protected communications.
Named “Raccoon,” the attack has been described as complex and the vulnerability is “very hard to exploit.” While most users should probably not be concerned about Raccoon, several major software vendors have released patches and mitigations to protect customers.
Raccoon can allow a man-in-the-middle (MitM) attacker to crack encrypted communications that could contain sensitive information. However, the attack is only successful if the targeted server reuses public Diffie-Hellman (DH) keys in the TLS handshake (i.e. the server uses static or ephemeral cipher suites such as TLS-DH or TLS-DHE), and if the attacker can conduct precise timing measurements.
“The attacker needs particular circumstances for the Raccoon attack to work,” the researchers wrote on a website dedicated to the Raccoon attack. “He needs to be close to the target server to perform high precision timing measurements. He needs the victim connection to use DH(E) and the server to reuse ephemeral keys. And finally, the attacker needs to observe the original connection.”
“For a real attacker, this is a lot to ask for. However, in comparison to what an attacker would need to do to break modern cryptographic primitives like AES, the attack does not look complex anymore. But still, a real-world attacker will probably use other attack vectors that are simpler and more reliable than this attack,” they explained.
The underlying vulnerability has existed for over 20 years, and it was fixed with the release of TLS 1.3.
Since this is a server-side vulnerability, there isn’t anything that clients can do to prevent attacks, except for ensuring that their web browsers don’t use the problematic ciph ..
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