CVE-2020-13817
Description
A high-performance ntpd instance that gets its time from unauthenticated IPv4 time sources may be vulnerable to an off-path attacker who can query time from the victim's ntpd instance. An attacker who can send a large number of packets with the spoofed IPv4 address of the upstream server can use this flaw to modify the victim's clock by a limited amount or cause ntpd to exit.
Statement
All versions of ntp package shipped with Red Hat Enterprise Linux are affected by this flaw. However several mitigations exists, please refer to the mitigation section for more details.
Mitigation
1. Have enough trustworthy sources of time.
2. If you are serving time to a possibly hostile network, have your system get its time from other than unauthenticated IPv4 over the hostile network.
3. Use NTP packet authentication where appropriate.
4. Pay attention to error messages logged by ntpd.
5. Monitor your ntpd instances. If the pstats command of ntpq shows the value for "bogus origin" is increasing then that association is likely under attack.
6. If you must get unauthenticated time over IPv4 on a hostile network, Use restrict ... noserve to prevent this attack (note that this is a heavy-handed protection), which blocks time service to the specified network.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.4 | 7.4 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Frequently Asked Questions
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