The DROWN attack, short for Decrypting RSA with Obsolete and Weakened encryption, is a significant vulnerability that targets servers supporting the outdated SSLv2 protocol. Despite SSLv2 being largely replaced by more secure protocols like SSLv3 and TLS, many servers still support it due to default settings or misconfigurations. This vulnerability allows attackers to decrypt secure HTTPS communications, potentially exposing sensitive information such as passwords, credit card numbers, and other confidential data.

How does a Drown Attack Work?

DROWN attacks exploit vulnerabilities in the SSLv2 protocol to decrypt secure communications. The attack begins by leveraging a server that supports both modern protocols like TLS and the outdated SSLv2. Attackers use a chosen-ciphertext attack, treating the SSLv2 server as a Bleichenbacher oracle. This involves manipulating the SSLv2 encrypted messages to reveal parts of the master secret, which is then used to decrypt the session key for a captured TLS handshake.

The process involves "trimming" the 48-byte SSLv3/TLS encrypted RSA ciphertext to fit into the SSLv2 ClientMasterKey message. The server interprets this as a 40-bit part of the SSLv2 master secret, with the remaining bits sent as plaintext. By brute-forcing the 40-bit encryption, attackers can decrypt the session key, allowing them to intercept and read secure communications.

There are two variants of the DROWN attack: the general and the special. The general attack requires significant computational resources, while the special attack exploits specific weaknesses in the OpenSSL implementation of SSLv2, making it feasible with modest computing power. This enables real-time man-in-the-middle attacks, significantly compromising the security of affected servers.

What are Examples of Drown Attacks?

Several high-profile websites have fallen victim to DROWN attacks, highlighting the widespread impact of this vulnerability. Notable examples include major platforms such as Yahoo, Alibaba, BuzzFeed, Flickr, and CNBC. These incidents underscore the critical need for organizations to update their security protocols and disable outdated SSLv2 support to prevent such breaches.

The DROWN vulnerability was publicly disclosed on March 1, 2016, revealing that approximately 33% of all HTTPS servers were susceptible to this attack. Despite the availability of patches and mitigation strategies, many websites remained vulnerable for weeks, demonstrating the challenges in promptly addressing security flaws across diverse and complex web infrastructures.

What are the Potential Risks of A Drown Attack?

The potential risks of suffering a DROWN attack are significant and multifaceted. Here are some of the key risks:

• Exposure of Sensitive Information: Attackers can decrypt communications, leading to the exposure of confidential data such as passwords, credit card numbers, and personal messages.

• Unauthorized Access: By hijacking user-to-browser communication, attackers can gain unauthorized access to sensitive systems and data, potentially leading to further breaches.

• Data Interception: Vulnerable servers can have their communications intercepted and decrypted, compromising the integrity and confidentiality of data exchanges.

• Operational Disruptions: Addressing the vulnerability may require significant operational changes, including server reconfigurations and potential downtime.

• Increased Susceptibility to Other Attacks: Supporting SSLv2 can make systems more vulnerable to additional attacks, such as man-in-the-middle attacks, due to the weakened security posture.

How can you Protect Against Drown Attacks?.

To protect against DROWN attacks, consider the following measures:

• Disable SSLv2: Ensure that SSLv2 is completely disabled on all servers, including web, SMTP, IMAP, and POP servers.

• Upgrade OpenSSL: Update to the latest version of OpenSSL, such as 1.0.2g or 1.0.1s, to mitigate vulnerabilities.

• Use Modern Protocols: Replace outdated encryption protocols like SSLv2 with secure alternatives such as TLS.

• Regular Software Updates: Keep all server software up-to-date to ensure that any security patches are applied promptly.

• Monitor Security Advisories: Stay informed about new vulnerabilities and apply recommended patches and updates as soon as they are released.