The OpenSSL Project announced on Thursday that more than a dozen vulnerabilities have been patched in OpenSSL with the release of versions 1.1.0a, 1.0.2i and 1.0.1u.
The latest versions of the cryptographic software library fix only one high severity issue. The flaw, tracked as CVE-2016-6304, can be exploited for denial-of-service (DoS) attacks by sending the targeted server an excessively large OCSP Status Request extension that causes memory exhaustion.
The OpenSSL Project has pointed out that the security hole affects servers in their default configuration even if they don’t support OCSP, but builds using the “no-ocsp” option are not impacted. Furthermore, servers using OpenSSL prior to 1.0.1g are not vulnerable in their default configuration.
The vulnerability was reported to OpenSSL developers by Shi Lei, a researcher at Chinese security firm Qihoo 360. The expert has been credited for finding many of the weaknesses patched this week.
OpenSSL 1.1.0, a branch that was launched less than one month ago, is affected by a moderate severity flaw (CVE-2016-6305) that can also be exploited for DoS attacks.
A total of 12 low severity vulnerabilities have also been resolved in the latest versions of OpenSSL. It’s worth noting that most of them don’t affect the 1.1.0 branch.
The list of low severity issues includes Sweet32, a recently disclosed birthday attack method against 64-bit block ciphers in TLS and OpenVPN (CVE-2016-2183). Researchers demonstrated that a network attacker who can monitor a long-lived HTTPS connection between a browser and a website might be able to recover HTTP cookies if they can capture a large volume of traffic.
OpenSSL has disabled the problematic ciphersuites in version 1.1.0, and moved them from the high to the medium cipherstring group in the 1.0.1 and 1.0.2 versions in an effort to prevent Sweet32 attacks.
Citrix also published a blog post this week detailing the Sweet32 attack method. The company noted that the attack is not easy to carry out, but advised customers to move away from DES ciphers and use AES instead.
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