{"id":"CVE-2026-64527","state":"PUBLISHED","title":"drm/hyperv: validate VMBus packet size in receive callback","description":"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->vid_hdr.type and dispatches into one\nof four message-type branches without knowing how many bytes the host\nwrote into hv->recv_buf. The completion path then runs\nmemcpy(hv->init_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->vid_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->recv_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().","publishedAt":"2026-07-25T09:20:51.078Z","updatedAt":"2026-07-25T09:20:51.078Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"57d5d697642e05d5dd2d40660817765943dd709f","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"f5251226551bfec98c4705641b6f94ff1f238d91","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"049a6b474823049fe60212f25f26e4b30f44ee8f","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"588c84b461393ff1998ac7b97b04f953f642e0df","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"164dc7bf17609340233c6bf4f66bb7c7008a0511","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"c8974d96b6a5496f33dc69a3ce28a7bf5078def4","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"7f87763f47a3c22fb50265a00619ef10f2394b18","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/hyperv/hyperv_drm_proto.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/hyperv/hyperv_drm_proto.c"]}],"references":["https://git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f","https://git.kernel.org/stable/c/f5251226551bfec98c4705641b6f94ff1f238d91","https://git.kernel.org/stable/c/049a6b474823049fe60212f25f26e4b30f44ee8f","https://git.kernel.org/stable/c/588c84b461393ff1998ac7b97b04f953f642e0df","https://git.kernel.org/stable/c/164dc7bf17609340233c6bf4f66bb7c7008a0511","https://git.kernel.org/stable/c/c8974d96b6a5496f33dc69a3ce28a7bf5078def4","https://git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64527.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64527","state":"PUBLISHED","datePublished":"2026-07-25T09:20:51.078Z","dateUpdated":"2026-07-25T09:20:51.078Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.794Z"},"containers":{"cna":{"title":"drm/hyperv: validate VMBus packet size in receive callback","descriptions":[{"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->vid_hdr.type and dispatches into one\nof four message-type branches without knowing how many bytes the host\nwrote into hv->recv_buf. The completion path then runs\nmemcpy(hv->init_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->vid_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->recv_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":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"57d5d697642e05d5dd2d40660817765943dd709f","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"f5251226551bfec98c4705641b6f94ff1f238d91","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"049a6b474823049fe60212f25f26e4b30f44ee8f","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"588c84b461393ff1998ac7b97b04f953f642e0df","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"164dc7bf17609340233c6bf4f66bb7c7008a0511","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"c8974d96b6a5496f33dc69a3ce28a7bf5078def4","versionType":"git"},{"version":"76c56a5affeba1e163b66b9d8cc192e6154466f0","status":"affected","lessThan":"7f87763f47a3c22fb50265a00619ef10f2394b18","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/hyperv/hyperv_drm_proto.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/hyperv/hyperv_drm_proto.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f"},{"url":"https://git.kernel.org/stable/c/f5251226551bfec98c4705641b6f94ff1f238d91"},{"url":"https://git.kernel.org/stable/c/049a6b474823049fe60212f25f26e4b30f44ee8f"},{"url":"https://git.kernel.org/stable/c/588c84b461393ff1998ac7b97b04f953f642e0df"},{"url":"https://git.kernel.org/stable/c/164dc7bf17609340233c6bf4f66bb7c7008a0511"},{"url":"https://git.kernel.org/stable/c/c8974d96b6a5496f33dc69a3ce28a7bf5078def4"},{"url":"https://git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-07-25T09:20:51.078Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.18.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.0.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}