In the Linux kernel, the following vulnerability has been resolved:
drm/hyperv: validate VMBus packet size in receive callback
hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one
of four message-type branches without knowing how many bytes the host
wrote into hv->recv_buf. The completion path then runs
memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that
wakes on wait_for_completion_timeout() can read up to 16 KiB of
residue from a prior message as if it were the response payload.
Pass bytes_recvd into hyperv_receive_sub() and reject any packet that
does not cover the pipe + synthvid header. A single switch on
msg->vid_hdr.type then computes the type-specific payload size: the
three completion-driving types (SYNTHVID_VERSION_RESPONSE,
SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through
to a shared exit that requires that size before memcpy/complete, while
SYNTHVID_FEATURE_CHANGE validates its own payload and returns before
reading is_dirt_needed. Unknown types are dropped.
SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills
resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT
array. Validate the fixed prefix first so resolution_count can be
read, bound it against the array, then require only the count-sized
array, so the shorter responses the host actually sends are accepted.
Only run the sub-handler when vmbus_recvpacket() returned success. The
memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE
only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead
reports the required length, which can exceed hv->recv_buf, so copying
bytes_recvd would read and write past the 16 KiB buffers. Gating on the
success return keeps the copy bounded. The nonzero-return path is itself
a malformed-message case and is now logged rather than silently skipped;
channel recovery is not attempted.
Rejected packets are reported via drm_err_ratelimited() rather than
silently dropped, matching the CoCo-hardened pattern in
hv_kvp_onchannelcallback().
drm/hyperv: validate VMBus packet size in receive callback
hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one
of four message-type branches without knowing how many bytes the host
wrote into hv->recv_buf. The completion path then runs
memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that
wakes on wait_for_completion_timeout() can read up to 16 KiB of
residue from a prior message as if it were the response payload.
Pass bytes_recvd into hyperv_receive_sub() and reject any packet that
does not cover the pipe + synthvid header. A single switch on
msg->vid_hdr.type then computes the type-specific payload size: the
three completion-driving types (SYNTHVID_VERSION_RESPONSE,
SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through
to a shared exit that requires that size before memcpy/complete, while
SYNTHVID_FEATURE_CHANGE validates its own payload and returns before
reading is_dirt_needed. Unknown types are dropped.
SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills
resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT
array. Validate the fixed prefix first so resolution_count can be
read, bound it against the array, then require only the count-sized
array, so the shorter responses the host actually sends are accepted.
Only run the sub-handler when vmbus_recvpacket() returned success. The
memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE
only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead
reports the required length, which can exceed hv->recv_buf, so copying
bytes_recvd would read and write past the 16 KiB buffers. Gating on the
success return keeps the copy bounded. The nonzero-return path is itself
a malformed-message case and is now logged rather than silently skipped;
channel recovery is not attempted.
Rejected packets are reported via drm_err_ratelimited() rather than
silently dropped, matching the CoCo-hardened pattern in
hv_kvp_onchannelcallback().
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
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Advisories
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Sat, 25 Jul 2026 10:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: drm/hyperv: validate VMBus packet size in receive callback hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one of four message-type branches without knowing how many bytes the host wrote into hv->recv_buf. The completion path then runs memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that wakes on wait_for_completion_timeout() can read up to 16 KiB of residue from a prior message as if it were the response payload. Pass bytes_recvd into hyperv_receive_sub() and reject any packet that does not cover the pipe + synthvid header. A single switch on msg->vid_hdr.type then computes the type-specific payload size: the three completion-driving types (SYNTHVID_VERSION_RESPONSE, SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through to a shared exit that requires that size before memcpy/complete, while SYNTHVID_FEATURE_CHANGE validates its own payload and returns before reading is_dirt_needed. Unknown types are dropped. SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT array. Validate the fixed prefix first so resolution_count can be read, bound it against the array, then require only the count-sized array, so the shorter responses the host actually sends are accepted. Only run the sub-handler when vmbus_recvpacket() returned success. The memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead reports the required length, which can exceed hv->recv_buf, so copying bytes_recvd would read and write past the 16 KiB buffers. Gating on the success return keeps the copy bounded. The nonzero-return path is itself a malformed-message case and is now logged rather than silently skipped; channel recovery is not attempted. Rejected packets are reported via drm_err_ratelimited() rather than silently dropped, matching the CoCo-hardened pattern in hv_kvp_onchannelcallback(). | |
| Title | drm/hyperv: validate VMBus packet size in receive callback | |
| 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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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-07-25T09:20:51.078Z
Reserved: 2026-07-19T15:36:31.794Z
Link: CVE-2026-64527
Vulnrichment
No data.
NVD
No data.
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.