CVE-2026-64527 (GCVE-0-2026-64527)

Vulnerability from cvelistv5 – Published: 2026-07-25 09:20 – Updated: 2026-07-25 09:20
VLAI
Title
drm/hyperv: validate VMBus packet size in receive callback
Summary
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().
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < 57d5d697642e05d5dd2d40660817765943dd709f (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < f5251226551bfec98c4705641b6f94ff1f238d91 (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < 049a6b474823049fe60212f25f26e4b30f44ee8f (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < 588c84b461393ff1998ac7b97b04f953f642e0df (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < 164dc7bf17609340233c6bf4f66bb7c7008a0511 (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < c8974d96b6a5496f33dc69a3ce28a7bf5078def4 (git)
Affected: 76c56a5affeba1e163b66b9d8cc192e6154466f0 , < 7f87763f47a3c22fb50265a00619ef10f2394b18 (git)
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Linux Linux Affected: 5.14
Unaffected: 0 , < 5.14 (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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{
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          "product": "Linux",
          "programFiles": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/hyperv: validate VMBus packet size in receive callback\n\nhyperv_receive_sub() reads msg-\u003evid_hdr.type and dispatches into one\nof four message-type branches without knowing how many bytes the host\nwrote into hv-\u003erecv_buf. The completion path then runs\nmemcpy(hv-\u003einit_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that\nwakes on wait_for_completion_timeout() can read up to 16 KiB of\nresidue from a prior message as if it were the response payload.\n\nPass bytes_recvd into hyperv_receive_sub() and reject any packet that\ndoes not cover the pipe + synthvid header. A single switch on\nmsg-\u003evid_hdr.type then computes the type-specific payload size: the\nthree completion-driving types (SYNTHVID_VERSION_RESPONSE,\nSYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through\nto a shared exit that requires that size before memcpy/complete, while\nSYNTHVID_FEATURE_CHANGE validates its own payload and returns before\nreading is_dirt_needed. Unknown types are dropped.\n\nSYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills\nresolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT\narray. Validate the fixed prefix first so resolution_count can be\nread, bound it against the array, then require only the count-sized\narray, so the shorter responses the host actually sends are accepted.\n\nOnly run the sub-handler when vmbus_recvpacket() returned success. The\nmemcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE\nonly on a successful receive; on -ENOBUFS vmbus_recvpacket() instead\nreports the required length, which can exceed hv-\u003erecv_buf, so copying\nbytes_recvd would read and write past the 16 KiB buffers. Gating on the\nsuccess return keeps the copy bounded. The nonzero-return path is itself\na malformed-message case and is now logged rather than silently skipped;\nchannel recovery is not attempted.\n\nRejected packets are reported via drm_err_ratelimited() rather than\nsilently dropped, matching the CoCo-hardened pattern in\nhv_kvp_onchannelcallback()."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-07-25T09:20:51.078Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f"
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        {
          "url": "https://git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18"
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      "title": "drm/hyperv: validate VMBus packet size in receive callback",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64527",
    "datePublished": "2026-07-25T09:20:51.078Z",
    "dateReserved": "2026-07-19T15:36:31.794Z",
    "dateUpdated": "2026-07-25T09:20:51.078Z",
    "state": "PUBLISHED"
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A single switch on\\nmsg-\u003evid_hdr.type then computes the type-specific payload size: the\\nthree completion-driving types (SYNTHVID_VERSION_RESPONSE,\\nSYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through\\nto a shared exit that requires that size before memcpy/complete, while\\nSYNTHVID_FEATURE_CHANGE validates its own payload and returns before\\nreading is_dirt_needed. Unknown types are dropped.\\n\\nSYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills\\nresolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT\\narray. Validate the fixed prefix first so resolution_count can be\\nread, bound it against the array, then require only the count-sized\\narray, so the shorter responses the host actually sends are accepted.\\n\\nOnly run the sub-handler when vmbus_recvpacket() returned success. The\\nmemcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE\\nonly on a successful receive; on -ENOBUFS vmbus_recvpacket() instead\\nreports the required length, which can exceed hv-\u003erecv_buf, so copying\\nbytes_recvd would read and write past the 16 KiB buffers. Gating on the\\nsuccess return keeps the copy bounded. The nonzero-return path is itself\\na malformed-message case and is now logged rather than silently skipped;\\nchannel recovery is not attempted.\\n\\nRejected packets are reported via drm_err_ratelimited() rather than\\nsilently dropped, matching the CoCo-hardened pattern in\\nhv_kvp_onchannelcallback().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"drivers/gpu/drm/hyperv/hyperv_drm_proto.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"57d5d697642e05d5dd2d40660817765943dd709f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"f5251226551bfec98c4705641b6f94ff1f238d91\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"049a6b474823049fe60212f25f26e4b30f44ee8f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"588c84b461393ff1998ac7b97b04f953f642e0df\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"164dc7bf17609340233c6bf4f66bb7c7008a0511\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"c8974d96b6a5496f33dc69a3ce28a7bf5078def4\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"76c56a5affeba1e163b66b9d8cc192e6154466f0\",\"lessThan\":\"7f87763f47a3c22fb50265a00619ef10f2394b18\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"drivers/gpu/drm/hyperv/hyperv_drm_proto.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.14\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.14\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.210\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.176\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.143\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.93\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.35\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.12\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/049a6b474823049fe60212f25f26e4b30f44ee8f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/164dc7bf17609340233c6bf4f66bb7c7008a0511\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/588c84b461393ff1998ac7b97b04f953f642e0df\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c8974d96b6a5496f33dc69a3ce28a7bf5078def4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f5251226551bfec98c4705641b6f94ff1f238d91\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.