CVE-2020-16166

The Linux kernel through 5.7.11 allows remote attackers to make observations that help to obtain sensitive information about the internal state of the network RNG, aka CID-f227e3ec3b5c. This is related to drivers/char/random.c and kernel/time/timer.c.

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/2020-08/msg00009.html
• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00047.html
• https://arxiv.org/pdf/2012.07432.pdf
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f227e3ec3b5cad859ad15666874405e8c1bbc1d4
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c51f8f88d705e06bd696d7510aff22b33eb8e638
• https://github.com/torvalds/linux/commit/f227e3ec3b5cad859ad15666874405e8c1bbc1d4
• https://lists.debian.org/debian-lts-announce/2020/09/msg00025.html
• https://lists.debian.org/debian-lts-announce/2020/10/msg00032.html
• https://lists.debian.org/debian-lts-announce/2020/10/msg00034.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AAPTLPAEKVAJYJ4LHN7VH4CN2W75R2YW/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MFBCLQWJI5I4G25TVJNLXLAXJ4MERQNW/
• https://security.netapp.com/advisory/ntap-20200814-0004/
• https://usn.ubuntu.com/4525-1/
• https://usn.ubuntu.com/4526-1/
• https://www.oracle.com/security-alerts/cpuApr2021.html