{"id":"CVE-2026-64034","state":"PUBLISHED","title":"net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer\n\nIn mana_hwc_rx_event_handler(), resp->response.hwc_msg_id is read from\nDMA-coherent memory and bounds-checked, then mana_hwc_handle_resp()\nre-reads the same field from the same DMA buffer for test_bit() and\npointer arithmetic.\n\nDMA-coherent memory is mapped uncacheable on x86 and is shared,\nunencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes\ndirectly to host-visible memory. A H/W can modify the value\nbetween the check and the use, bypassing the bounds validation.\n\nFix this by reading hwc_msg_id exactly once using READ_ONCE() into a\nstack-local variable in mana_hwc_rx_event_handler(), and passing the\nvalidated value as a parameter to mana_hwc_handle_resp().","publishedAt":"2026-07-19T15:39:23.470Z","updatedAt":"2026-10-19T20:28:09.897Z","severity":{"score":9.3,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"a201c66edf2ebc6cfdc3813a889ba20fecebfae3","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"70ad2dff8d052a85dfef15715b531f38a29108cf","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"566f42fb67a7ebfed6650e407e5b72e6b3e83bf7","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"6180a06bbc99fd9114b8db4be6c4d46e40f046ef","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"09ec063d87c2dd3fa6f3561361a017bd882e9f37","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"3c4db56ccd13dd020fbf43afabaee74a40ec75e4","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"35f0f0a2536a4d604b4dbad92c85c4a8fdebb870","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microsoft/mana/hw_channel.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.209","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.142","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","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/net/ethernet/microsoft/mana/hw_channel.c"]}],"references":["https://git.kernel.org/stable/c/a201c66edf2ebc6cfdc3813a889ba20fecebfae3","https://git.kernel.org/stable/c/70ad2dff8d052a85dfef15715b531f38a29108cf","https://git.kernel.org/stable/c/566f42fb67a7ebfed6650e407e5b72e6b3e83bf7","https://git.kernel.org/stable/c/6180a06bbc99fd9114b8db4be6c4d46e40f046ef","https://git.kernel.org/stable/c/09ec063d87c2dd3fa6f3561361a017bd882e9f37","https://git.kernel.org/stable/c/3c4db56ccd13dd020fbf43afabaee74a40ec75e4","https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870"],"weaknesses":["CWE-367"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64034.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64034","state":"PUBLISHED","datePublished":"2026-07-19T15:39:23.470Z","dateUpdated":"2026-10-19T20:28:09.897Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.028Z"},"containers":{"cna":{"title":"net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer\n\nIn mana_hwc_rx_event_handler(), resp->response.hwc_msg_id is read from\nDMA-coherent memory and bounds-checked, then mana_hwc_handle_resp()\nre-reads the same field from the same DMA buffer for test_bit() and\npointer arithmetic.\n\nDMA-coherent memory is mapped uncacheable on x86 and is shared,\nunencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes\ndirectly to host-visible memory. A H/W can modify the value\nbetween the check and the use, bypassing the bounds validation.\n\nFix this by reading hwc_msg_id exactly once using READ_ONCE() into a\nstack-local variable in mana_hwc_rx_event_handler(), and passing the\nvalidated value as a parameter to mana_hwc_handle_resp()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"a201c66edf2ebc6cfdc3813a889ba20fecebfae3","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"70ad2dff8d052a85dfef15715b531f38a29108cf","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"566f42fb67a7ebfed6650e407e5b72e6b3e83bf7","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"6180a06bbc99fd9114b8db4be6c4d46e40f046ef","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"09ec063d87c2dd3fa6f3561361a017bd882e9f37","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"3c4db56ccd13dd020fbf43afabaee74a40ec75e4","versionType":"git"},{"version":"ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f","status":"affected","lessThan":"35f0f0a2536a4d604b4dbad92c85c4a8fdebb870","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microsoft/mana/hw_channel.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.209","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.142","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","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/net/ethernet/microsoft/mana/hw_channel.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a201c66edf2ebc6cfdc3813a889ba20fecebfae3"},{"url":"https://git.kernel.org/stable/c/70ad2dff8d052a85dfef15715b531f38a29108cf"},{"url":"https://git.kernel.org/stable/c/566f42fb67a7ebfed6650e407e5b72e6b3e83bf7"},{"url":"https://git.kernel.org/stable/c/6180a06bbc99fd9114b8db4be6c4d46e40f046ef"},{"url":"https://git.kernel.org/stable/c/09ec063d87c2dd3fa6f3561361a017bd882e9f37"},{"url":"https://git.kernel.org/stable/c/3c4db56ccd13dd020fbf43afabaee74a40ec75e4"},{"url":"https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":9.3,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:L - Exploitation requires a malicious hypervisor or host that can modify MANA HWC DMA-coherent response buffers between guest kernel loads; it is not reachable by sending network packets to the guest's data path.\nAC:L - The attacker controlling the hypervisor fully controls DMA buffer contents and can reliably flip hwc_msg_id between the validation read and the use in mana_hwc_handle_resp() on uncacheable coherent memory.\nPR:N - The attacking hypervisor needs no guest OS credentials or capabilities; exploitation targets the guest kernel through the virtual device DMA path while the MANA driver is active.\nUI:N - No victim user action is required beyond normal Azure VM operation with the MANA driver loaded and HWC receive buffers posted.\nS:C - The vulnerability crosses the VM/DMA security boundary by allowing a hostile hypervisor to corrupt guest kernel memory that the confidential-guest threat model assumes is protected from host tampering.\nC:H - Out-of-bounds indexing via bypassed hwc_msg_id validation enables reading adjacent kernel heap objects through misdirected caller_ctx access and test_bit() on the inflight bitmap.\nI:H - Host-controlled response data is copied with memcpy() to an out-of-bounds output_buf pointer, enabling arbitrary kernel memory corruption and potential control-flow hijacking.\nA:H - Out-of-bounds caller_ctx access and corrupted completion signaling can cause kernel oops, panic, or hang during HWC response handling."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:38:28.529Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"5.15.209"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.1.175"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.6.142"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.12.92"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64034","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:35:42.542411Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-367","lang":"en","type":"CWE","description":"CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:28:09.897Z"}}]}}}