Linux Kernel up to 5.17.12/5.18.1 __try_cmpxchg_user random values

Summaryinfo

A vulnerability classified as problematic was found in Linux Kernel up to 5.17.12/5.18.1. Affected is the function __try_cmpxchg_user. Such manipulation leads to random values. This vulnerability is traded as CVE-2022-49562. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 5.17.12/5.18.1. Affected by this issue is the function __try_cmpxchg_user. The manipulation with an unknown input leads to a random values vulnerability. Using CWE to declare the problem leads to CWE-330. The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. Impacted is confidentiality. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits Use the recently introduced __try_cmpxchg_user() to update guest PTE A/D bits instead of mapping the PTE into kernel address space. The VM_PFNMAP path is broken as it assumes that vm_pgoff is the base pfn of the mapped VMA range, which is conceptually wrong as vm_pgoff is the offset relative to the file and has nothing to do with the pfn. The horrific hack worked for the original use case (backing guest memory with /dev/mem), but leads to accessing "random" pfns for pretty much any other VM_PFNMAP case.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2022-49562 since 02/26/2025. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1600.001.

The vulnerability scanner Nessus provides a plugin with the ID 237278 (Alibaba Cloud Linux 3 : 0075: cloud-kernel bugfix, enhancement and (ALINUX3-SA-2025:0075)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.17.13 or 5.18.2 eliminates this vulnerability. Applying the patch 38b888911e8dc89b89d8147cfb1d2dbe6373bf78/8089e5e1d18402fb8152d6b6815450a36fffa9b0/f122dfe4476890d60b8c679128cd2259ec96a24c is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (237278). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.17.0
• 5.17.1
• 5.17.2
• 5.17.3
• 5.17.4
• 5.17.5
• 5.17.6
• 5.17.7
• 5.17.8
• 5.17.9
• 5.17.10
• 5.17.11
• 5.17.12
• 5.18.0
• 5.18.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion