{"id":"CVE-2026-72135","summary":"tpm: Make the TPM character devices non-seekable","details":"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-\u003ef_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.","modified":"2026-08-18T03:56:54.696929682Z","published":"2026-08-15T05:53:10.315Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72135.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/21a13f932972bc9836f58c44fcd47c62abdecd95"},{"type":"WEB","url":"https://git.kernel.org/stable/c/232dcf908eb7eb9d8046a9597975caf44270966e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/947b773caaa548672184df025271b29bdc80b0f1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9c513dabd4540f811585a2087f23069767a284da"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dda695fab5e21f923d29e8cb01df256468ddfbd1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ed0ffc2c016629e40ba041ed0424a772d8b02e2c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f20d61c22bcaf172d6790b6500e3838e532e71c8"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72135.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72135"},{"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":"9488585b21bef0df1217e510c7134905d1d376a7"},{"fixed":"ed0ffc2c016629e40ba041ed0424a772d8b02e2c"},{"fixed":"232dcf908eb7eb9d8046a9597975caf44270966e"},{"fixed":"dda695fab5e21f923d29e8cb01df256468ddfbd1"},{"fixed":"9c513dabd4540f811585a2087f23069767a284da"},{"fixed":"21a13f932972bc9836f58c44fcd47c62abdecd95"},{"fixed":"ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed"},{"fixed":"947b773caaa548672184df025271b29bdc80b0f1"},{"fixed":"f20d61c22bcaf172d6790b6500e3838e532e71c8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72135.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72135.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}