What We Do
How we do it
Resources
SECURITY ADVISORIES
Jul 26, 2021
PetitPotam NTLM Relay Attack
THE THREAT PetitPotam is a variant of NTLM Relay attacks discovered by security researcher Gilles Lionel. Proof of Concept code released last week [1] relies on the Encrypting File System Remote (EFSRPC) protocol to provoke a Windows host into performing an NTLM authentication request against an attacker-controlled server, exposing NTLM authentication details or authentication certificates.…
Read More
View all Advisories →
Company
ABOUT eSENTIRE
About Us
eSentire is The Authority in Managed Detection and Response Services, protecting the critical data and applications of 1000+ organizations in 70+ countries from known and unknown cyber threats. Founded in 2001, the company’s mission is to hunt, investigate and stop cyber threats before they become business disrupting events.
Read about how we got here
Leadership Work at eSentire
LATEST PRESS RELEASE
Jul 12, 2021
Tecala and eSentire Partner to Protect Enterprises across APAC from Business-Disrupting Cyber Attacks
Sydney, 12 July, 2021 - Tecala, Australia’s award-winning technology services and IT consulting provider, today announced it has chosen eSentire, the global Authority in Managed Detection and Response (MDR) cybersecurity services, as their exclusive MDR solution provider in Australia and New Zealand. This partnership will enable Tecala to augment its cybersecurity practice and offer enterprises…
Read More
Partners
PARTNER PROGRAM
Partners
Our award-winning partner program offers financial rewards, sales and marketing tools and personalized training. Accelerate your business and grow your revenue by offering our world-class Managed Detection and Response (MDR) services.
Learn about our Partner Program
Resources
Security advisories — Feb 27, 2019

EFAIL – Vulnerabilities in PGP and S/MIME Encrypted Emails

2 min read

Two new vulnerabilities have been discovered impacting multiple email clients. The vulnerabilities impact customers that use OpenPGP or S/MIME to secure email communications. Successful exploitation may allow threat actors to decrypt sensitive email communications when the victim is using a vulnerable email client or plugin. Threat actors combine known weaknesses in the encryption algorithms with automatic rendering of active content to perform this new attack. Threat actors first need to obtain the encrypted messages, then send them to a user with a vulnerable email client.

What we’re doing about it

What you should do about it

Additional information

For a full list of affected email clients, please see the official EFAIL whitepaper1.

There are two techniques for exploiting EFAIL. The first being direct exfiltration which affects both PGP and S/MIME. In this scenario, the adversary intercepts an encrypted email and places it into a new email with HTML tags around the encrypted section. This new email is then sent to the victim. When received by the victim’s mail client, the message is unencrypted, but the additional HTML tags cause a misinterpretation of data, sending the unencrypted message to a remote server where it can be read.

The second technique is the modification of ciphertext using known weaknesses in the Cipher Block Chaining. Since threat actors know the structure of S/MIME emails, they can perform a plaintext attack and embed HTML tags, similar to the first technique.

CVE-2017-176882 and CVE-2017-176893 have been reserved for the PGP and S/MIME vulnerabilities; at this time, the CVE references have not been updated with current information.


References:

[1] Efail: Breaking S/MIME and OpenPGP Email Encryption
https://efail.de/efail-attack-paper.pdf

[2] CVE-2017-17688
https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-17688

[3] CVE-2017-17689
https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-17689