{"id":"CVE-2026-72151","state":"PUBLISHED","title":"tpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt\n\ntpm_buf_append_salt() in drivers/char/tpm/tpm2-sessions.c calls\ncrypto_kpp_generate_public_key() and crypto_kpp_compute_shared_secret()\nwithout installing a completion callback, discards both return values,\nand immediately frees the kpp_request via kpp_request_free(). When the\nresolved ecdh-nist-p256 KPP backend is asynchronous (atmel-ecc, HPRE,\nkeembay-ocs), either operation returns -EINPROGRESS and the deferred\ncompletion worker dereferences the freed request.\n\nThe path fires automatically from the hwrng_fillfn kernel thread via\ntpm_get_random -> tpm2_get_random -> tpm2_start_auth_session ->\ntpm_buf_append_salt on every entropy poll, without any userland action.\n\nInstall crypto_req_done as the completion callback, wrap both KPP\noperations in crypto_wait_req(), and propagate errors to the caller.\nThe wait is a no-op for synchronous backends.","publishedAt":"2026-08-15T05:53:22.196Z","updatedAt":"2026-08-17T05:41:00.459Z","severity":{"score":8.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"111e520efbe82b324bc42b1999b723c0619eea6d","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"934d1cd40e2893bf7a041b54f6afd1c008d7a21c","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"493333f167926c7adab8e7563e21ad71d8af84fa","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"73851a7c43dfa52d2ed9415889b33daf85da0ed9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm2-sessions.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm2-sessions.c"]}],"references":["https://git.kernel.org/stable/c/111e520efbe82b324bc42b1999b723c0619eea6d","https://git.kernel.org/stable/c/934d1cd40e2893bf7a041b54f6afd1c008d7a21c","https://git.kernel.org/stable/c/493333f167926c7adab8e7563e21ad71d8af84fa","https://git.kernel.org/stable/c/73851a7c43dfa52d2ed9415889b33daf85da0ed9"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72151.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72151","state":"PUBLISHED","datePublished":"2026-08-15T05:53:22.196Z","dateUpdated":"2026-08-17T05:41:00.459Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.908Z"},"containers":{"cna":{"title":"tpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt\n\ntpm_buf_append_salt() in drivers/char/tpm/tpm2-sessions.c calls\ncrypto_kpp_generate_public_key() and crypto_kpp_compute_shared_secret()\nwithout installing a completion callback, discards both return values,\nand immediately frees the kpp_request via kpp_request_free(). When the\nresolved ecdh-nist-p256 KPP backend is asynchronous (atmel-ecc, HPRE,\nkeembay-ocs), either operation returns -EINPROGRESS and the deferred\ncompletion worker dereferences the freed request.\n\nThe path fires automatically from the hwrng_fillfn kernel thread via\ntpm_get_random -> tpm2_get_random -> tpm2_start_auth_session ->\ntpm_buf_append_salt on every entropy poll, without any userland action.\n\nInstall crypto_req_done as the completion callback, wrap both KPP\noperations in crypto_wait_req(), and propagate errors to the caller.\nThe wait is a no-op for synchronous backends."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"111e520efbe82b324bc42b1999b723c0619eea6d","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"934d1cd40e2893bf7a041b54f6afd1c008d7a21c","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"493333f167926c7adab8e7563e21ad71d8af84fa","versionType":"git"},{"version":"1085b8276bb4239daa7008f0dcd5c973e4bd690f","status":"affected","lessThan":"73851a7c43dfa52d2ed9415889b33daf85da0ed9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm2-sessions.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm2-sessions.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/111e520efbe82b324bc42b1999b723c0619eea6d"},{"url":"https://git.kernel.org/stable/c/934d1cd40e2893bf7a041b54f6afd1c008d7a21c"},{"url":"https://git.kernel.org/stable/c/493333f167926c7adab8e7563e21ad71d8af84fa"},{"url":"https://git.kernel.org/stable/c/73851a7c43dfa52d2ed9415889b33daf85da0ed9"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable code is reached only via local kernel TPM/HWRNG paths (hwrng_fillfn kernel thread polling tpm_get_random, or local /dev/hwrng reads); there is no network, adjacent-radio, or physical-access entry point to tpm_buf_append_salt.\nAC:L - On affected builds (CONFIG_TCG_TPM2_HMAC plus an async ecdh-nist-p256 backend), the UAF is deterministically triggered each auth-session setup without winning a race; async KPP returns -EINPROGRESS and the completion worker later dereferences the already-freed kpp_request.\nPR:N - No attacker credentials are required: the hwrng kernel thread invokes tpm2_start_auth_session automatically on TPM RNG polls, and unprivileged local processes can also reach tpm_get_random via /dev/hwrng without root or namespaced admin capabilities.\nUI:N - Exploitation does not require any victim user action such as mounting a filesystem or opening a file; the bug fires from background kernel entropy collection and TPM session setup without interactive steps.\nS:U - Impact is confined to kernel memory integrity and availability on the same host; it is a standard kernel heap UAF, not a cross-boundary escape such as guest-to-host VM breakout or IOMMU/DMA bypass.\nC:H - Use-after-free of a kmalloc'd kpp_request lets an attacker influence freed heap contents and potentially obtain arbitrary kernel memory read primitives through heap grooming, not merely a bounded leak.\nI:H - The UAF corrupts kernel heap metadata/object lifetimes and can be leveraged for arbitrary write or control-flow hijack (privilege escalation), not just limited or transient data modification.\nA:H - The deferred crypto completion dereferences freed memory, causing kernel oops/panic or hang during normal TPM RNG polling, yielding complete loss of system availability on affected hardware."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:41:00.459Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}