CVE-2019-19922

kernel/sched/fair.c in the Linux kernel before 5.3.9, when cpu.cfs_quota_us is used (e.g., with Kubernetes), allows attackers to cause a denial of service against non-cpu-bound applications by generating a workload that triggers unwanted slice expiration, aka CID-de53fd7aedb1. (In other words, although this slice expiration would typically be seen with benign workloads, it is possible that an attacker could calculate how many stray requests are required to force an entire Kubernetes cluster into a low-performance state caused by slice expiration, and ensure that a DDoS attack sent that number of stray requests. An attack does not affect the stability of the kernel; it only causes mismanagement of application execution.)

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.3.9
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=de53fd7aedb100f03e5d2231cfce0e4993282425
• https://github.com/kubernetes/kubernetes/issues/67577
• https://github.com/torvalds/linux/commit/de53fd7aedb100f03e5d2231cfce0e4993282425
• https://lists.debian.org/debian-lts-announce/2020/01/msg00013.html
• https://relistan.com/the-kernel-may-be-slowing-down-your-app
• https://security.netapp.com/advisory/ntap-20200204-0002/
• https://usn.ubuntu.com/4226-1/
• https://www.oracle.com/security-alerts/cpuApr2021.html
• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.3.9
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=de53fd7aedb100f03e5d2231cfce0e4993282425
• https://github.com/kubernetes/kubernetes/issues/67577
• https://github.com/torvalds/linux/commit/de53fd7aedb100f03e5d2231cfce0e4993282425
• https://lists.debian.org/debian-lts-announce/2020/01/msg00013.html
• https://relistan.com/the-kernel-may-be-slowing-down-your-app
• https://security.netapp.com/advisory/ntap-20200204-0002/
• https://usn.ubuntu.com/4226-1/
• https://www.oracle.com/security-alerts/cpuApr2021.html