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.
References
Configurations
Configuration 1 (hide)
|
History
14 Jul 2026, 20:19
| Type | Values Removed | Values Added |
|---|---|---|
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* |
|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.8 |
| First Time |
Linux linux Kernel
Linux |
|
| CWE | CWE-129 | |
| References | () https://git.kernel.org/stable/c/01b71b930f15728aa8599478a7ce90c19dcd9fc2 - Patch | |
| References | () https://git.kernel.org/stable/c/0d419c23bb11b5c9664de777c47c1f04a235882d - Patch | |
| References | () https://git.kernel.org/stable/c/0eb281eb95b2d4eea4db1da5fe91023aecc97095 - Patch | |
| References | () https://git.kernel.org/stable/c/577a8d3bae0531f0e5ccfac919cd8192f920a804 - Patch | |
| References | () https://git.kernel.org/stable/c/74f1a22f7a80f03d28ad8551a2d25d563433addf - Patch | |
| References | () https://git.kernel.org/stable/c/b315b033a877b1ee6d827810b5d7bb4392ffcf8d - Patch | |
| References | () https://git.kernel.org/stable/c/ecf9b3ea7847fe14f34b8c41f00de1eb95c747da - Patch | |
| References | () https://access.redhat.com/security/cve/CVE-2026-52969 - Third Party Advisory | |
| References | () https://bugzilla.redhat.com/show_bug.cgi?id=2492434 - Third Party Advisory | |
| References | () https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52969.json - Third Party Advisory |
30 Jun 2026, 03:20
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.0 |
| CWE | CWE-190 | |
| References |
|
24 Jun 2026, 17:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-06-24 17:17
Updated : 2026-07-15 01:16
NVD link : CVE-2026-52969
Mitre link : CVE-2026-52969
CVE.ORG link : CVE-2026-52969
JSON object : View
Products Affected
linux
- linux_kernel