CVE-2020-10761: 
NixOS vulnerability analysis and mitigation

An assertion failure vulnerability was discovered in the Network Block Device (NBD) Server component of QEMU versions prior to 5.0.1. The vulnerability was identified as CVE-2020-10761 and was discovered by Eric Blake and Xueqiang Wei of Red Hat. The issue was introduced in QEMU v4.2 when changes were made to allow nbd-client to send longer export names (OpenWall, NVD).

The vulnerability occurs when an nbd-client sends a spec-compliant request that is near the boundary of maximum permitted request length. The CVSS v3.1 base score for this vulnerability is 5.0 (Medium) with the vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L. The vulnerability is classified as CWE-617 (Reachable Assertion) (NVD, Ubuntu).

When successfully exploited, this vulnerability allows a remote nbd-client to crash the qemu-nbd server, resulting in a denial of service (DoS). The impact is limited to availability, with no direct effect on confidentiality or integrity of the system (NVD, NetApp).

The vulnerability is exploitable remotely and requires low attack complexity. The attacker needs low privileges and no user interaction to exploit this vulnerability. The attack can be initiated by sending specifically crafted requests near the maximum permitted length boundary (NVD).

The vulnerability was fixed in QEMU version 5.0.1. Users are advised to upgrade to this version or later. For systems that cannot be immediately upgraded, no alternative workarounds are available. Various Linux distributions have released security updates to address this vulnerability, including Ubuntu, SUSE, and Gentoo (Ubuntu, Gentoo).