2021-38199 | Linux Kernel connection-setup Order nfs4client.c denial of service

By Max On Aug 14, 2021

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.6	$0-$5k	0.11

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 5.13.3 (Operating System). Affected by this issue is an unknown function of the file fs/nfs/nfs4client.c of the component connection-setup Order Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. Impacted is availability.

The weakness was disclosed 08/09/2021 as dd99e9f98fbf423ff6d365b37a98e8879170f17c. The advisory is available at github.com. This vulnerability is handled as CVE-2021-38199 since 08/08/2021. The exploitation is known to be easy. The attack may be launched remotely. The successful exploitation requires a simple authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/14/2021). This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 5.13.4 eliminates this vulnerability. The upgrade is hosted for download at cdn.kernel.org. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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