Description
The symmetric-key feature in the receive function in ntp_proto.c in ntpd in NTP 3.x and 4.x before 4.2.8p2 performs state-variable updates upon receiving certain invalid packets, which makes it easier for man-in-the-middle attackers to cause a denial of service (synchronization loss) by spoofing the source IP address of a peer.
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-6 | — |
| Debian 7 | ntp | 1:4.2.6.p5+dfsg-2+deb7u4 | DSA-3223-1 |
| Debian 6.0 | ntp | 1:4.2.6.p2+dfsg-1+deb6u3 | DLA-192-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 14.04 LTS | ntp | 1:4.2.6.p5+dfsg-3ubuntu2.14.04.3 | USN-2567-1 |
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 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 | ntp | 4.2.6p5-44.1 | SUSE-SU-2015:0865-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 | ntp | 4.2.6p5-44.1 | SUSE-SU-2015:0865-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | ntp | 4.2.8p9-1.1 | openSUSE-SU-2024:10181-1 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | ntp +4 | 4.2.6p5-22.el7 | ELSA-2015-2231 |
Advisories 8
- 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
- DLA-192-1 ntp - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-3223-1 ntp - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-2567-1 ntp vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- openSUSE-SU-2024:10181-1 ntp-4.2.8p9-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2015:0865-1 Security update for ntp SUSE / openSUSE Security Updates · Feb 4, 2026
- ELSA-2015-2231 Moderate: ntp security, bug fix, and enhancement update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Nov 23, 2015
References
- DSA-3222 vendor-advisory
- 20150408 Network Time Protocol Daemon Symmetric Mode Packet Processing Denial of Service Vulnerability vendor-advisory
- [chrony-announce] 20150407 chrony-1.31.1 released (security) mailing-list
- USN-2567-1 vendor-advisory
- VU#374268 third-party-advisory
- 73950 vdb-entry
- SSRT102029 vendor-advisory
- FEDORA-2015-5761 vendor-advisory
- http://support.ntp.org/bin/view/Main/SecurityNotice#Recent_Vulnerabilities
- https://kc.mcafee.com/corporate/index?page=content&id=SB10114
- FEDORA-2015-5874 vendor-advisory
- APPLE-SA-2015-06-30-2 vendor-advisory
- openSUSE-SU-2015:0775 vendor-advisory
- http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
- GLSA-201509-01 vendor-advisory
- MDVSA-2015:202 vendor-advisory
- http://www.oracle.com/technetwork/topics/security/bulletinapr2015-2511959.html
- http://support.apple.com/kb/HT204942
- HPSBHF03557 vendor-advisory
- RHSA-2015:1459 vendor-advisory
- http://bugs.ntp.org/show_bug.cgi?id=2781
- 20150408 Multiple Vulnerabilities in ntpd (April 2015) Affecting Cisco Products vendor-advisory
- DSA-3223 vendor-advisory
- 1032031 vdb-entry