NULL pointer dereference in Xen - CVE-2020-29571

Vulnerability details

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isn't protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.

Affected software

How to mitigate CVE-2020-29571

External References

• https://www.debian.org/security/2020/dsa-4812
• https://xenbits.xenproject.org/xsa/advisory-359.html

Related Security Bulletins

• NULL pointer dereference in Xen
• NULL pointer dereference in xen (Alpine package)
• Debian update for xen
• Fedora 33 update for xen
• Fedora 32 update for xen