libgcrypt before version 1.7.8 is vulnerable to a cache side-channel attack resulting into a complete break of RSA-1024 while using the left-to-right method for computing the sliding-window expansion. The same attack is believed to work on RSA-2048 with moderately more computation. This side-channel requires that attacker can run arbitrary software on the hardware where the private RSA key is used.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-7526
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-7526
• https://eprint.iacr.org/2017/627
• https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=78130828e9a140a9de4dafadbc844dbb64cb709a
• https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=8725c99ffa41778f382ca97233183bcd687bb0ce
• https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=e6a3dc9900433bbc8ad362a595a3837318c28fa9
• https://lists.gnupg.org/pipermail/gnupg-announce/2017q2/000408.html
• https://usn.ubuntu.com/3733-1/
• https://usn.ubuntu.com/3733-2/
• https://www.debian.org/security/2017/dsa-3901
• https://www.debian.org/security/2017/dsa-3960
• http://www.securityfocus.com/bid/99338
• http://www.securitytracker.com/id/1038915