CVE-2015-3193: Infoleak
The following was reported by OpenSSL upstream:
There is a carry propagating bug in the x8664 Montgomery squaring procedure. No EC algorithms are affected. Analysis suggests that attacks against RSA and DSA as a result of this defect would be very difficult to perform and are not believed likely. Attacks against DH are considered just feasible (although very difficult) because most of the work necessary to deduce information about a private key may be performed offline. The amount of resources required for such an attack would be very significant and likely only accessible to a limited number of attackers. An attacker would additionally need online access to an unpatched system using the target private key in a scenario with persistent DH parameters and a private key that is shared between multiple clients. For example this can occur by default in OpenSSL DHE based SSL/TLS ciphersuites.
This issue affects OpenSSL version 1.0.2.
OpenSSL 1.0.2 users should upgrade to 1.0.2e
This issue was reported to OpenSSL on August 13 2015 by Hanno Böck. The fix was developed by Andy Polyakov of the OpenSSL development team.
Other sources
The Montgomery squaring implementation in crypto/bn/asm/x8664-mont5.pl in OpenSSL 1.0.2 before 1.0.2e on the x8664 platform, as used by the BNmodexp function, mishandles carry propagation and produces incorrect output, which makes it easier for remote attackers to obtain sensitive private-key information via an attack against use of a (1) Diffie-Hellman (DH) or (2) Diffie-Hellman Ephemeral (DHE) ciphersuite.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2015-3193?
CVE-2015-3193 is considered a low severity vulnerability due to the difficulty of exploiting the carry propagating bug.
How do I fix CVE-2015-3193?
To fix CVE-2015-3193, update OpenSSL to a version that is not affected by this vulnerability.
Which versions of OpenSSL are affected by CVE-2015-3193?
CVE-2015-3193 affects OpenSSL versions from 1.0.2 through 1.0.2d.
Are DSA and EC algorithms affected by CVE-2015-3193?
No, EC algorithms are not affected by CVE-2015-3193.
What type of bug is identified in CVE-2015-3193?
CVE-2015-3193 identifies a carry propagating bug in the x86_64 Montgomery squaring procedure.