There's a vulnerability in common forms of email encryption

Posted May 15, 2018

Critical unpatched vulnerabilities in widely-used email encryption tools PGP and S/MIME have been discovered by a team led by Sebastian Schinzel, professor of Computer Security at the Münster University of Applied Sciences.

The flaw, codenamed EFAIL, if exploited, allow an attacker to decrypt sent or received messages, according to the researcher team. Professor of computer security at Münster Sebastian Schinzel wrote on Twitter that "there are now no reliable fixes for the vulnerability".

The vulnerability, dubbed EFAIL, exploits flaws in the way some email clients handle PGP and S/MIME encrypted messages.

Specifically, the group urged everyone to temporarily disable these mail client encryption add-ons: Enigmail for Thunderbird, GPGTools for Apple Mail, and Gpg4win for Outlook. They suggest there will be more on the story released tomorrow and they did suggest that all of these companies that use PGP have been previously warned of this situation.

This is then encrypted with the sender's private "key" and decrypted by the receiver using a separate public key.

Keith Lee, the founder of a LawyerSmack, an online legal community, says: "The most [lawyers] are doing is using GSuite or some equivalent and relying on that in transit encryption, but are rarely (if ever) actually encrypting the text/content of emails".

The encryption program PGP (Pretty Good Privacy) was seen as the gold standard for email encryption, and was developed in 1991. The EFF's report only indicated that a vulnerability existed, and that users should disable PGP plugins in their mail clients until patches are deployed.

The EFF echoed Schnizel's instruction, and advised those affected to use Signal - a free end-to-end encryption software that's compatible with both Android and iOS devices - until the issue has been rectified. There are other methods that could be used to attack the information, but these backchannels are more hard to exploit. EFF has a write up on this also with all the links you need if reading Twitter is not your thing.

Some have been arguing that EFAIL isn't a problem for OpenPGP as long as the implementations are done correctly (in addition to the aforementioned authenticated encryption, this includes not using HTML emails, which thwarts the problem).

But while that advice might be easier to implement for anyone who uses and configures their own PGP tools, it fails to address how secure webmail providers might address the flaws.

"There are now no reliable fixes for the vulnerability", Schinzel tweeted Monday morning. "In 2018, businesses must re-evaluate how they communicate, opting to phase out email for secure communications solutions that are open-source, independently audited and end-to-end encrypted".