{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "76c56a5affeba1e163b66b9d8cc192e6154466f0"
            },
            {
              "fixed": "57d5d697642e05d5dd2d40660817765943dd709f"
            },
            {
              "fixed": "f5251226551bfec98c4705641b6f94ff1f238d91"
            },
            {
              "fixed": "049a6b474823049fe60212f25f26e4b30f44ee8f"
            },
            {
              "fixed": "588c84b461393ff1998ac7b97b04f953f642e0df"
            },
            {
              "fixed": "164dc7bf17609340233c6bf4f66bb7c7008a0511"
            },
            {
              "fixed": "c8974d96b6a5496f33dc69a3ce28a7bf5078def4"
            },
            {
              "fixed": "7f87763f47a3c22fb50265a00619ef10f2394b18"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.14.0"
            },
            {
              "fixed": "5.15.210"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.176"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.143"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.93"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.35"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.0.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64527.json"
  },
  "details": "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().",
  "id": "CVE-2026-64527",
  "modified": "2026-07-27T03:56:29.737717853Z",
  "published": "2026-07-25T09:20:51.078Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/049a6b474823049fe60212f25f26e4b30f44ee8f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/164dc7bf17609340233c6bf4f66bb7c7008a0511"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/588c84b461393ff1998ac7b97b04f953f642e0df"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c8974d96b6a5496f33dc69a3ce28a7bf5078def4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f5251226551bfec98c4705641b6f94ff1f238d91"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64527.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64527"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.8.0",
  "summary": "drm/hyperv: validate VMBus packet size in receive callback"
}