Arch Linux Security Advisory ASA-201701-37 ========================================== Severity: Medium Date : 2017-01-28 CVE-ID : CVE-2016-7055 CVE-2017-3731 CVE-2017-3732 Package : openssl Type : multiple issues Remote : Yes Link : https://security.archlinux.org/AVG-154 Summary ======= The package openssl before version 1.0.2.k-1 is vulnerable to multiple issues including denial of service, incorrect calculation and information disclosure. Resolution ========== Upgrade to 1.0.2.k-1. # pacman -Syu "openssl>=1.0.2.k-1" The problems have been fixed upstream in version 1.0.2.k. Workaround ========== None. Description =========== - CVE-2016-7055 (incorrect calculation) There is a carry propagating bug in the Broadwell-specific Montgomery multiplication procedure that handles input lengths divisible by, but longer than 256 bits. Analysis suggests that attacks against RSA, DSA and DH private keys are impossible. This is because the subroutine in question is not used in operations with the private key itself and an input of the attacker's direct choice. Otherwise the bug can manifest itself as transient authentication and key negotiation failures or reproducible erroneous outcome of public-key operations with specially crafted input. Among EC algorithms only Brainpool P-512 curves are affected and one presumably can attack ECDH key negotiation. Impact was not analyzed in detail, because pre-requisites for attack are considered unlikely. Namely multiple clients have to choose the curve in question and the server has to share the private key among them, neither of which is default behavior. Even then only clients that chose the curve will be affected. - CVE-2017-3731 (denial of service) If an SSL/TLS server or client is running on a 32-bit host, and a specific cipher is being used, then a truncated packet can cause that server or client to perform an out-of-bounds read, usually resulting in a crash. For OpenSSL 1.1.0, the crash can be triggered when using CHACHA20/POLY1305; users should upgrade to 1.1.0d. For Openssl 1.0.2, the crash can be triggered when using RC4-MD5; users who have not disabled that algorithm should update to 1.0.2k. - CVE-2017-3732 (information disclosure) There is a carry propagating bug in the x86_64 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. Note: This issue is very similar to CVE-2015-3193 but must be treated as a separate problem. Impact ====== A remote attacker is able to crash the application, access sensitive information or transiently authenticate against the server. References ========== https://www.openssl.org/news/secadv/20161110.txt https://www.openssl.org/news/secadv/20170126.txt https://github.com/openssl/openssl/commit/57c4b9f6a2f800b41ce2836986fe33640f... https://security.archlinux.org/CVE-2016-7055 https://security.archlinux.org/CVE-2017-3731 https://security.archlinux.org/CVE-2017-3732