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.
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.
Advisories
| Source | ID | Title |
|---|---|---|
Debian DLA |
DLA-4665-1 | linux security update |
Debian DLA |
DLA-4671-1 | linux-6.1 security update |
Ubuntu USN |
USN-8566-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8567-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8568-1 | Linux kernel (OEM) vulnerabilities |
Ubuntu USN |
USN-8569-1 | Linux kernel (HWE) vulnerabilities |
Ubuntu USN |
USN-8574-1 | Linux kernel (GCP FIPS) vulnerabilities |
Ubuntu USN |
USN-8575-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8576-1 | Linux kernel (NVIDIA Tegra) vulnerabilities |
Ubuntu USN |
USN-8593-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8574-2 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8595-1 | Linux kernel (Oracle) vulnerabilities |
Ubuntu USN |
USN-8596-1 | Linux kernel (NVIDIA) vulnerabilities |
Ubuntu USN |
USN-8575-2 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8576-2 | Linux kernel (NVIDIA Tegra) vulnerabilities |
Ubuntu USN |
USN-8575-3 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8595-2 | Linux kernel (AWS) vulnerabilities |
Ubuntu USN |
USN-8603-1 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-8606-1 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-8607-1 | Linux kernel (Azure CVM) vulnerabilities |
Ubuntu USN |
USN-8608-1 | Linux kernel (Azure FIPS) vulnerabilities |
Ubuntu USN |
USN-8609-1 | Linux kernel (Azure CVM) vulnerabilities |
Ubuntu USN |
USN-8610-1 | Linux kernel (Azure CVM) vulnerabilities |
Ubuntu USN |
USN-8574-3 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8595-3 | Linux kernel (AWS) vulnerabilities |
Ubuntu USN |
USN-8618-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8619-1 | Linux kernel (HWE) vulnerabilities |
Ubuntu USN |
USN-8620-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-8620-2 | Linux kernel (Azure FIPS) vulnerabilities |
Ubuntu USN |
USN-8620-3 | Linux kernel (Intel IoTG) vulnerabilities |
Ubuntu USN |
USN-8620-4 | Linux kernel (Intel IoTG) vulnerabilities |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 26 Jun 2026 03:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-125 |
Fri, 26 Jun 2026 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Wed, 24 Jun 2026 18:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-125 CWE-190 |
Wed, 24 Jun 2026 17:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | KVM: Reject wrapped offset in kvm_reset_dirty_gfn() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-07-15T02:48:28.368Z
Reserved: 2026-06-09T07:44:35.375Z
Link: CVE-2026-52969
No data.
No data.
OpenCVE Enrichment
Updated: 2026-06-26T05:45:04Z
Weaknesses
Debian DLA
Ubuntu USN