CVE-2020-13817

ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows remote attackers to cause a denial of service (daemon exit or system time change) by predicting transmit timestamps for use in spoofed packets. The victim must be relying on unauthenticated IPv4 time sources. There must be an off-path attacker who can query time from the victims ntpd instance.

Weakness

The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Affected Software

Potential Mitigations

• Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds.
• In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
• Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a “random enough” number.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/112.html
• https://cwe.mitre.org/data/definitions/485.html
• https://cwe.mitre.org/data/definitions/59.html

References

• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
• http://support.ntp.org/bin/view/Main/NtpBug3596
• https://bugs.ntp.org/show_bug.cgi?id=3596
• https://security.gentoo.org/glsa/202007-12
• https://security.netapp.com/advisory/ntap-20200625-0004/
• https://www.oracle.com/security-alerts/cpujan2022.html