{"id":"CVE-2026-64527","summary":"drm/hyperv: validate VMBus packet size in receive callback","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().","modified":"2026-07-27T04:03:22.904938646Z","published":"2026-07-25T09:20:51.078Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64527.json","cna_assigner":"Linux"},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"76c56a5affeba1e163b66b9d8cc192e6154466f0"},{"fixed":"57d5d697642e05d5dd2d40660817765943dd709f"},{"fixed":"f5251226551bfec98c4705641b6f94ff1f238d91"},{"fixed":"049a6b474823049fe60212f25f26e4b30f44ee8f"},{"fixed":"588c84b461393ff1998ac7b97b04f953f642e0df"},{"fixed":"164dc7bf17609340233c6bf4f66bb7c7008a0511"},{"fixed":"c8974d96b6a5496f33dc69a3ce28a7bf5078def4"},{"fixed":"7f87763f47a3c22fb50265a00619ef10f2394b18"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64527.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","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"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64527.json"}}],"schema_version":"1.7.5"}