CONFERENCE On Demand: Cyber AI & Automation Summit - Watch Now
Connect with us

Hi, what are you looking for?



OpenSSL Patches TLS Flaw Exposing Many HTTPS Servers

The OpenSSL Project has released updates to patch several vulnerabilities in the crypto library, including a high severity TLS issue that can be exploited to crack encrypted communications and steal potentially sensitive data.

The OpenSSL Project has released updates to patch several vulnerabilities in the crypto library, including a high severity TLS issue that can be exploited to crack encrypted communications and steal potentially sensitive data.

A team of researchers has published a paper on “DROWN” (Decrypting RSA with Obsolete and Weakened eNcryption), a cross-protocol attack method that involves SSLv2, an old version of the protocol that is still supported by many servers.

The vulnerability, tracked as CVE-2016-0800, is believed to affect a quarter of the top one million HTTPS domains and one-third of all HTTPS websites.

“A typical scenario requires the attacker to observe 1,000 TLS handshakes, then initiate 40,000 SSLv2 connections and perform 2^50 offline work to decrypt a 2048-bit RSA TLS ciphertext,” researchers explained in their paper. “We implemented the attack and can decrypt a TLS 1.2 handshake using 2048-bit RSA in under 8 hours using Amazon EC2, at a cost of $440.”

A cheaper version of the attack, which can be used to decrypt a TLS ciphertext in roughly one minute on a fast CPU, involves a couple of OpenSSL vulnerabilities: CVE-2015-3197, which was fixed in OpenSSL 1.0.1r and 1.0.2f, and CVE-2016-0703, a newly discovered flaw that was unknowingly patched in March 2015.

According to experts, a majority of servers vulnerable to DROWN attacks are also affected by these OpenSSL bugs. An Internet scan has shown that more than 2.3 million HTTPS servers with browser-trusted certificates are vulnerable.

“This form of the attack is fast enough to allow an online man-in-the-middle (MitM) style of attack, where the attacker can impersonate a vulnerable server to the victim client. Among other advantages, such an attacker can force the client and server to use RSA key exchange (and can then decrypt the connection) even if they would normally prefer a different cipher,” researchers explained. “This lets the attacker target and break connections between modern browsers and servers that prefer perfect-forward-secret key exchange methods, such as DHE and ECDH.”

After being notified by researchers, the OpenSSL Project released OpenSSL 1.0.2g and 1.0.1s, which disable SSLv2 by default at build-time and ensure that it’s impossible to configure a TLS server so that it’s vulnerable to DROWN attacks.

Advertisement. Scroll to continue reading.

Microsoft IIS and the Network Security Services (NSS) library have SSLv2 support disabled by default. Researchers have issued a series of recommendations for Apache, Postfix and Nginx users.

In addition to patching the DROWN issue, the OpenSSL Project addressed several low and medium severity vulnerabilities with the release of versions 1.0.2g and 1.0.1s, including a double-free issue in DSA code (CVE-2016-0705), a memory leak in SRP database lookups (CVE-2016-0798), BN_hex2bn/BN_dec2bn function NULL pointer corruption flaws (CVE-2016-0797), memory issues in BIO_*printf functions (CVE-2016-0799), and a side channel attack on modular exponentiation (CVE-2016-0702).

Written By

Eduard Kovacs (@EduardKovacs) is a managing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join us as we delve into the transformative potential of AI, predictive ChatGPT-like tools and automation to detect and defend against cyberattacks.


As cybersecurity breaches and incidents escalate, the cyber insurance ecosystem is undergoing rapid and transformational change.


Expert Insights

Related Content


Less than a week after announcing that it would suspended service indefinitely due to a conflict with an (at the time) unnamed security researcher...

Data Breaches

OpenAI has confirmed a ChatGPT data breach on the same day a security firm reported seeing the use of a component affected by an...

Risk Management

The supply chain threat is directly linked to attack surface management, but the supply chain must be known and understood before it can be...

IoT Security

A group of seven security researchers have discovered numerous vulnerabilities in vehicles from 16 car makers, including bugs that allowed them to control car...


A researcher at IOActive discovered that home security systems from SimpliSafe are plagued by a vulnerability that allows tech savvy burglars to remotely disable...


Patch Tuesday: Microsoft calls attention to a series of zero-day remote code execution attacks hitting its Office productivity suite.


Patch Tuesday: Microsoft warns vulnerability (CVE-2023-23397) could lead to exploitation before an email is viewed in the Preview Pane.


The latest Chrome update brings patches for eight vulnerabilities, including seven reported by external researchers.