Description
The read_network_packet function in ntp_io.c in ntpd in NTP 4.x before 4.2.8p1 on Linux and OS X does not properly determine whether a source IP address is an IPv6 loopback address, which makes it easier for remote attackers to spoof restricted packets, and read or write to the runtime state, by leveraging the ability to reach the ntpd machine's network interface with a packet from the ::1 address.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 11 | ntp | 1:4.2.6.p5+dfsg-4 | — |
| Debian 7 | ntp | 1:4.2.6.p5+dfsg-2+deb7u2 | DSA-3154-1 |
| Debian 6.0 | ntp | 1:4.2.6.p2+dfsg-1+deb6u2 | DLA-149-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | ntp +4 | 4.2.6p5-22.el7 | RHSA-2015:2231 |
| RHEL 6 | ntp +3 | 4.2.6p5-5.el6 | RHSA-2015:1459 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | ntp +4 | 4.2.6p5-22.el7 | ELSA-2015-2231 |
Advisories 5
- RHSA-2015:2231 Red Hat Security Advisory: ntp security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2015:1459 Red Hat Security Advisory: ntp security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-3154-1 ntp - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-149-1 ntp - security update Debian Security (DSA / DLA) · Mar 9, 2026
- ELSA-2015-2231 Moderate: ntp security, bug fix, and enhancement update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Nov 23, 2015
References
- VU#852879 third-party-advisory
- http://support.ntp.org/bin/view/Main/SecurityNotice#December_2014_NTP_Security_Vulne
- http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
- http://bugs.ntp.org/show_bug.cgi?id=2672
- DSA-3388 vendor-advisory
- 72584 vdb-entry
- RHSA-2015:1459 vendor-advisory
- https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03886en_us
- https://bugzilla.redhat.com/show_bug.cgi?id=1184572