OpenSSL Security Advisory - Cross-protocol attack on TLS using SSLv2 (DROWN) (CVE-2016-0800)
12 April 2016 03:35 PM


On March 1, 2016, a vulnerability in OpenSSL named DROWN, a man-in-the-middle attack that stands for “Decrypting RSA with Obsolete and Weakened eNcryption", was announced. All MarkLogic Server versions 5.0 and later are *not* affected by this vulnerability.


The Advisory reported by states

CVE-2016-0800 (OpenSSL advisory)  [High severity] 1st March 2016: 

A cross-protocol attack was discovered that could lead to decryption of TLS sessions by using a server supporting SSLv2 and EXPORT cipher suites as a Bleichenbacher RSA padding oracle. Note that traffic between clients and non-vulnerable servers can be decrypted provided another server supporting SSLv2 and EXPORT ciphers (even with a different protocol such as SMTP, IMAP or POP) shares the RSA keys of the non-vulnerable server. This vulnerability is known as DROWN (CVE-2016-0800). Recovering one session key requires the attacker to perform approximately 2^50 computation, as well as thousands of connections to the affected server. A more efficient variant of the DROWN attack exists against unpatched OpenSSL servers using versions that predate 1.0.2a, 1.0.1m, 1.0.0r and 0.9.8zf released on 19/Mar/2015 (see CVE-2016-0703 below). Users can avoid this issue by disabling the SSLv2 protocol in all their SSL/TLS servers, if they've not done so already. Disabling all SSLv2 ciphers is also sufficient, provided the patches for CVE-2015-3197 (fixed in OpenSSL 1.0.1r and 1.0.2f) have been deployed. Servers that have not disabled the SSLv2 protocol, and are not patched for CVE-2015-3197 are vulnerable to DROWN even if all SSLv2 ciphers are nominally disabled, because malicious clients can force the use of SSLv2 with EXPORT ciphers. OpenSSL 1.0.2g and 1.0.1s deploy the following mitigation against DROWN: SSLv2 is now by default disabled at build-time. Builds that are not configured with "enable-ssl2" will not support SSLv2. Even if "enable-ssl2" is used, users who want to negotiate SSLv2 via the version-flexible SSLv23_method() will need to explicitly call either of: SSL_CTX_clear_options(ctx, SSL_OP_NO_SSLv2); or SSL_clear_options(ssl, SSL_OP_NO_SSLv2); as appropriate. Even if either of those is used, or the application explicitly uses the version-specific SSLv2_method() or its client or server variants, SSLv2 ciphers vulnerable to exhaustive search key recovery have been removed. Specifically, the SSLv2 40-bit EXPORT ciphers, and SSLv2 56-bit DES are no longer available. In addition, weak ciphers in SSLv3 and up are now disabled in default builds of OpenSSL. Builds that are not configured with "enable-weak-ssl-ciphers" will not provide any "EXPORT" or "LOW" strength ciphers. Reported by Nimrod Aviram and Sebastian Schinzel.

Fixed in OpenSSL 1.0.1s (Affected 1.0.1r, 1.0.1q, 1.0.1p, 1.0.1o, 1.0.1n, 1.0.1m, 1.0.1l, 1.0.1k, 1.0.1j, 1.0.1i, 1.0.1h, 1.0.1g, 1.0.1f, 1.0.1e, 1.0.1d, 1.0.1c, 1.0.1b, 1.0.1a, 1.0.1)

Fixed in OpenSSL 1.0.2g (Affected 1.0.2f, 1.0.2e, 1.0.2d, 1.0.2c, 1.0.2b, 1.0.2a, 1.0.2)

MarkLogic Server Details

Marklogic Server disallows SSLv2 and disallows weak ciphers in all supported version.  As a result, MarkLogic Server is not affected by this vulverability.

Whenever MarkLogic releases a new version of MarkLogic Server, OpenSSL versions are reviewed and updated. 


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