# CVE-2026-52969: KVM: Reject wrapped offset in kvm_reset_dirty_gfn()

> A local attacker with access to /dev/kvm can exploit an integer overflow in KVM dirty ring handling to achieve out-of-bounds memory access and potential privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Jun 2026
- **Updated:** 15 Jul 2026
- **Also known as:** BELL-CVE-2026-52969, DEBIAN-CVE-2026-52969, GHSA-gpq6-rrxf-v33x, ROOT-OS-DEBIAN-12-CVE-2026-52969, ROOT-OS-UBUNTU-2204-CVE-2026-52969, ROOT-OS-UBUNTU-2404-CVE-2026-52969, UBUNTU-CVE-2026-52969

## What is CVE-2026-52969?

CVE-2026-52969 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

KVM: Reject wrapped offset in kvm_reset_dirty_gfn()

kvm_reset_dirty_gfn() guards the gfn range with

	if (!memslot || (offset + __fls(mask)) >= memslot->npages)
		return;

but offset is u64 and the addition is unchecked.  The check can be
silently bypassed by a u64 wrap.

The dirty ring backing those entries is MAP_SHARED at
KVM_DIRTY_LOG_PAGE_OFFSET of the vcpu fd, so the VMM can rewrite the
slot and offset fields of any entry between when the kernel pushes
them and when KVM_RESET_DIRTY_RINGS consumes them.  On reset,
kvm_dirty_ring_reset() re-reads the values via READ_ONCE() and feeds
them straight back into this check; only the flags handshake is
treated as the handover, the slot/offset payload is taken on trust.

Crafting two entries

	entry[i].offset   = 0xffffffffffffffc1
	entry[i+1].offset = 0

makes the coalescing loop in kvm_dirty_ring_reset() compute

	delta = (s64)(0 - 0xffffffffffffffc1) = 63

which falls in [0, BITS_PER_LONG), so it folds entry[i+1] into the
existing mask by setting bit 63.  The trailing kvm_reset_dirty_gfn()
call then sees offset = 0xffffffffffffffc1 and __fls(mask) = 63;
the sum is 0 in u64 and the bounds check passes.

That offset propagates into kvm_arch_mmu_enable_log_dirty_pt_masked()
unchanged.  On the legacy MMU path -- kvm_memslots_have_rmaps() ==
true, i.e. shadow paging, any VM that has allocated shadow roots, or
a write-tracked slot -- it reaches gfn_to_rmap(), which indexes
slot->arch.rmap[0][] with a near-U64_MAX gfn.  That is an
out-of-bounds load of a kvm_rmap_head, followed by a conditional
clear of PT_WRITABLE_MASK in whatever the loaded pointer points at.
The path is reachable from any process holding /dev/kvm.

Range-check offset on its own first, so the addition cannot wrap.
memslot->npages is bounded well below U64_MAX, so once offset <
npages holds, offset + __fls(mask) (with __fls(mask) < BITS_PER_LONG)
stays in range.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-52969?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52969?

Apply the vendor's patch.

## Is CVE-2026-52969 being exploited?

There is no known exploitation of CVE-2026-52969 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52969 and fix it if it is affected.

What it is: CVE-2026-52969 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-52969 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-52969/ (Markdown: https://insights.sbomify.com/CVE-2026-52969/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52969
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52969
- OSV: https://osv.dev/vulnerability/CVE-2026-52969

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52969/
Summaries are generated and may contain mistakes; the official description above is the record.