A stack-based buffer overflow was found in the way ntpd processed 'ntpdc reslist' commands that queried restriction lists with a large amount of entries. A remote attacker could use this flaw to crash the ntpd process. Upstream patch (which also addresses CVE-2015-7977): https://github.com/ntp-project/ntp/commit/8a0c765f3c47633fa262356b0818788d1cf249b1
External References: http://support.ntp.org/bin/view/Main/SecurityNotice#January_2016_NTP_4_2_8p6_Securit http://www.talosintel.com/reports/TALOS-2016-0075/
Created ntp tracking bugs for this issue: Affects: fedora-all [bug 1300277]
Similar to CVE-2015-7977, to exploit this issue, the attacker has to rely on two factors: * ntpd to be configured to receive mode 7 packets. By default on Red Hat Enterprise Linux, ntpd is configured to receive this packets only on localhost. * the restriction list must contain a large number of entries (more than 5000). When the number of entries is large enough, ntpd will crash due to stack exhaustion while recursively traversing the list. Since the attacker has no way of influencing the size of the restriction list by adding more entries, it is quite unlikely to exploit this issue. Having such a large number of restriction entries would also be an uncommon configuration since it would be more practical to restrict connecting clients via other means (e.g. iptables) should the system require it. Statement: This issue affects the versions of ntp as shipped with Red Hat Enterprise Linux 5, 6, and 7. Red Hat Product Security has rated this issue as having Moderate security impact. A future update may address this issue in Red Hat Enterprise Linux 6 and 7. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.
Mitigation: Keep the number of restriction list entries in ntp.conf lower than 500.
ntp-4.2.6p5-36.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
ntp-4.2.6p5-36.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
This issue has been addressed in the following products: Red Hat Enterprise Linux 6 Via RHSA-2016:0780 https://rhn.redhat.com/errata/RHSA-2016-0780.html
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2016:2583 https://rhn.redhat.com/errata/RHSA-2016-2583.html