{"id":"CVE-2026-72135","state":"PUBLISHED","title":"tpm: Make the TPM character devices non-seekable","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntpm: Make the TPM character devices non-seekable\n\nThe TPM character devices expose a sequential command/response\ninterface, but their open handlers leave FMODE_PREAD and FMODE_PWRITE\nenabled.\n\nAfter a command leaves a response pending, pread(fd, buf, 16, 0x1400)\npasses 0x1400 as *off to tpm_common_read(). The transfer length is\nbounded by response_length, but the offset is used unchecked when\nforming data_buffer + *off. A sufficiently large offset therefore causes\nan out-of-bounds heap read through copy_to_user() and, if the copy\nsucceeds, an out-of-bounds zero-write through the following memset().\n\nPositional I/O does not provide coherent semantics for this interface.\nAn arbitrary pread offset cannot represent how much of a response has\nbeen consumed sequentially. The write callback always stores a command\nat the start of data_buffer, while pwrite() does not update file->f_pos\nand can leave the sequential read cursor stale.\n\nCall nonseekable_open() from both open handlers. This removes\nFMODE_PREAD and FMODE_PWRITE, causing positional reads and writes to\nfail with -ESPIPE before reaching the TPM callbacks, and explicitly\nmarks the files non-seekable. Normal read() and write() continue to use\nthe existing sequential f_pos cursor, leaving the response state machine\nunchanged.\n\nTested on Linux 6.12 with KASAN and a swtpm TPM2 device:\n\n - sequential partial reads returned the complete response\n - pread() and preadv() with offset 0x1400 returned -ESPIPE\n - pwrite() and pwritev() with offset zero returned -ESPIPE\n - the pending response remained intact after the rejected operations\n - a subsequent normal command/response cycle completed normally\n - no KASAN report was produced.","publishedAt":"2026-08-15T05:53:10.315Z","updatedAt":"2026-10-16T18:44:58.643Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/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":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"ed0ffc2c016629e40ba041ed0424a772d8b02e2c","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"232dcf908eb7eb9d8046a9597975caf44270966e","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"dda695fab5e21f923d29e8cb01df256468ddfbd1","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"9c513dabd4540f811585a2087f23069767a284da","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"21a13f932972bc9836f58c44fcd47c62abdecd95","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"947b773caaa548672184df025271b29bdc80b0f1","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"f20d61c22bcaf172d6790b6500e3838e532e71c8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm-dev.c","drivers/char/tpm/tpmrm-dev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","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/tpm-dev.c","drivers/char/tpm/tpmrm-dev.c"]}],"references":["https://git.kernel.org/stable/c/ed0ffc2c016629e40ba041ed0424a772d8b02e2c","https://git.kernel.org/stable/c/232dcf908eb7eb9d8046a9597975caf44270966e","https://git.kernel.org/stable/c/dda695fab5e21f923d29e8cb01df256468ddfbd1","https://git.kernel.org/stable/c/9c513dabd4540f811585a2087f23069767a284da","https://git.kernel.org/stable/c/21a13f932972bc9836f58c44fcd47c62abdecd95","https://git.kernel.org/stable/c/ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed","https://git.kernel.org/stable/c/947b773caaa548672184df025271b29bdc80b0f1","https://git.kernel.org/stable/c/f20d61c22bcaf172d6790b6500e3838e532e71c8"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72135.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72135","state":"PUBLISHED","datePublished":"2026-08-15T05:53:10.315Z","dateUpdated":"2026-10-16T18:44:58.643Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.907Z"},"containers":{"cna":{"title":"tpm: Make the TPM character devices non-seekable","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntpm: Make the TPM character devices non-seekable\n\nThe TPM character devices expose a sequential command/response\ninterface, but their open handlers leave FMODE_PREAD and FMODE_PWRITE\nenabled.\n\nAfter a command leaves a response pending, pread(fd, buf, 16, 0x1400)\npasses 0x1400 as *off to tpm_common_read(). The transfer length is\nbounded by response_length, but the offset is used unchecked when\nforming data_buffer + *off. A sufficiently large offset therefore causes\nan out-of-bounds heap read through copy_to_user() and, if the copy\nsucceeds, an out-of-bounds zero-write through the following memset().\n\nPositional I/O does not provide coherent semantics for this interface.\nAn arbitrary pread offset cannot represent how much of a response has\nbeen consumed sequentially. The write callback always stores a command\nat the start of data_buffer, while pwrite() does not update file->f_pos\nand can leave the sequential read cursor stale.\n\nCall nonseekable_open() from both open handlers. This removes\nFMODE_PREAD and FMODE_PWRITE, causing positional reads and writes to\nfail with -ESPIPE before reaching the TPM callbacks, and explicitly\nmarks the files non-seekable. Normal read() and write() continue to use\nthe existing sequential f_pos cursor, leaving the response state machine\nunchanged.\n\nTested on Linux 6.12 with KASAN and a swtpm TPM2 device:\n\n - sequential partial reads returned the complete response\n - pread() and preadv() with offset 0x1400 returned -ESPIPE\n - pwrite() and pwritev() with offset zero returned -ESPIPE\n - the pending response remained intact after the rejected operations\n - a subsequent normal command/response cycle completed normally\n - no KASAN report was produced."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"ed0ffc2c016629e40ba041ed0424a772d8b02e2c","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"232dcf908eb7eb9d8046a9597975caf44270966e","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"dda695fab5e21f923d29e8cb01df256468ddfbd1","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"9c513dabd4540f811585a2087f23069767a284da","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"21a13f932972bc9836f58c44fcd47c62abdecd95","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"947b773caaa548672184df025271b29bdc80b0f1","versionType":"git"},{"version":"9488585b21bef0df1217e510c7134905d1d376a7","status":"affected","lessThan":"f20d61c22bcaf172d6790b6500e3838e532e71c8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/tpm/tpm-dev.c","drivers/char/tpm/tpmrm-dev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","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/tpm-dev.c","drivers/char/tpm/tpmrm-dev.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ed0ffc2c016629e40ba041ed0424a772d8b02e2c"},{"url":"https://git.kernel.org/stable/c/232dcf908eb7eb9d8046a9597975caf44270966e"},{"url":"https://git.kernel.org/stable/c/dda695fab5e21f923d29e8cb01df256468ddfbd1"},{"url":"https://git.kernel.org/stable/c/9c513dabd4540f811585a2087f23069767a284da"},{"url":"https://git.kernel.org/stable/c/21a13f932972bc9836f58c44fcd47c62abdecd95"},{"url":"https://git.kernel.org/stable/c/ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed"},{"url":"https://git.kernel.org/stable/c/947b773caaa548672184df025271b29bdc80b0f1"},{"url":"https://git.kernel.org/stable/c/f20d61c22bcaf172d6790b6500e3838e532e71c8"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Exploitation requires local pread()/write() syscalls on /dev/tpm0 or /dev/tpmrm0 character devices; there is no network, Bluetooth, or physical-bus code path to the vulnerable tpm_common_read() handler.\nAC:L - An attacker who can open the device reliably triggers the bug by writing any TPM command to create a pending response, then calling pread() with a large offset; no races or special memory layout are required.\nPR:L - Upstream tpm2-tss udev rules grant non-root users in the tss group read/write access to /dev/tpmrm0 (mode 0660), which is the standard TPM2 user-space interface on laptops and servers with TPM hardware.\nUI:N - No victim interaction is required; the attacker opens the TPM device, submits a command, and issues the malicious pread() themselves without relying on another user to mount, click, or configure anything.\nS:U - The vulnerability corrupts kernel heap memory in the TPM driver on the same host; it does not by itself cross a VM, container, or IOMMU security boundary to affect a different trust domain.\nC:H - Unchecked pread offsets cause copy_to_user() to read beyond the 4096-byte data_buffer into adjacent kmalloc slab memory (including tpm_space pointers), leaking kernel heap contents to userspace.\nI:H - A successful out-of-bounds pread also executes memset() past data_buffer, zeroing adjacent heap objects such as tpm_space session/context pointers and enabling further memory corruption or control-flow manipulation.\nA:H - KASAN reports slab-out-of-bounds faults on both the copy_to_user read and memset write; 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