The following flaw was found in ntpd: An error handling logic error exists within ntpd that manifests due to improper error condition handling associated with certain crypto-NAK packets. An unauthenticated, off-path attacker can force ntpd processes on targeted servers to peer with time sources of the attacker's choosing by transmitting symmetric active crypto-NAK packets to ntpd. This attack bypasses the authentication typically required to establish a peer association and allows an attacker to make arbitrary changes to system time. External References: http://talosintel.com/reports/TALOS-2015-0069/ http://support.ntp.org/bin/view/Main/SecurityNotice#October_2015_NTP_Security_Vulner
Created ntp tracking bugs for this issue: Affects: fedora-all [bug 1274351]
Statement: This issue did not affect the versions of ntp as shipped with Red Hat Enterprise Linux 5, 6, and 7.
Upstream patch: https://github.com/ntp-project/ntp/commit/aa44b5835d69d8ee031736bb8ee2730a514edb7d
The 4.2.6 version of NTP is not vulnerable because while the ephemeral association can be created, it's immediately removed in the following code by the unpeer() call: /* * If this is a crypto_NAK, the server cannot authenticate a * client packet. The server might have just changed keys. Clear * the association and restart the protocol. */ if (is_authentic == AUTH_CRYPTO) { report_event(PEVNT_AUTH, peer, "crypto_NAK"); peer->flash |= TEST5; /* bad auth */ peer->badauth++; if (peer->flags & FLAG_PREEMPT) { unpeer(peer); return; } While the ephemeral association can be temporarily established, it does not allow for exploitation in any way.
ntp-4.2.6p5-34.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
ntp-4.2.6p5-34.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.
ntp-4.2.6p5-36.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.