---
id: CVE-2026-72135
title: 'tpm: Make the TPM character devices non-seekable'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tpm: Make the TPM character devices non-seekable

  The TPM character devices expose a sequential command/response
  interface, but their open handlers leave FMODE_PREAD an…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    ed0ffc2c016629e40ba041ed0424a772d8b02e2c
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    232dcf908eb7eb9d8046a9597975caf44270966e
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    dda695fab5e21f923d29e8cb01df256468ddfbd1
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    9c513dabd4540f811585a2087f23069767a284da
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    21a13f932972bc9836f58c44fcd47c62abdecd95
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    947b773caaa548672184df025271b29bdc80b0f1
  - >-
    Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 <
    f20d61c22bcaf172d6790b6500e3838e532e71c8
  - Linux 5.0
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:42:38.338660Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:44:58.643Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72135'
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'
tags:
  - cve.org
epss: 0.00169
epssPercentile: 0.05787
ingestedAt: '2026-10-16T19:46:24.428Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

tpm: Make the TPM character devices non-seekable

The TPM character devices expose a sequential command/response
interface, but their open handlers leave FMODE_PREAD and FMODE_PWRITE
enabled.

After a command leaves a response pending, pread(fd, buf, 16, 0x1400)
passes 0x1400 as *off to tpm_common_read(). The transfer length is
bounded by response_length, but the offset is used unchecked when
forming data_buffer + *off. A sufficiently large offset therefore causes
an out-of-bounds heap read through copy_to_user() and, if the copy
succeeds, an out-of-bounds zero-write through the following memset().

Positional I/O does not provide coherent semantics for this interface.
An arbitrary pread offset cannot represent how much of a response has
been consumed sequentially. The write callback always stores a command
at the start of data_buffer, while pwrite() does not update file->f_pos
and can leave the sequential read cursor stale.

Call nonseekable_open() from both open handlers. This removes
FMODE_PREAD and FMODE_PWRITE, causing positional reads and writes to
fail with -ESPIPE before reaching the TPM callbacks, and explicitly
marks the files non-seekable. Normal read() and write() continue to use
the existing sequential f_pos cursor, leaving the response state machine
unchanged.

Tested on Linux 6.12 with KASAN and a swtpm TPM2 device:

 - sequential partial reads returned the complete response
 - pread() and preadv() with offset 0x1400 returned -ESPIPE
 - pwrite() and pwritev() with offset zero returned -ESPIPE
 - the pending response remained intact after the rejected operations
 - a subsequent normal command/response cycle completed normally
 - no KASAN report was produced.

## Affected

- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < ed0ffc2c016629e40ba041ed0424a772d8b02e2c`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < 232dcf908eb7eb9d8046a9597975caf44270966e`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < dda695fab5e21f923d29e8cb01df256468ddfbd1`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < 9c513dabd4540f811585a2087f23069767a284da`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < 21a13f932972bc9836f58c44fcd47c62abdecd95`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < 947b773caaa548672184df025271b29bdc80b0f1`
- `Linux >= 9488585b21bef0df1217e510c7134905d1d376a7 < f20d61c22bcaf172d6790b6500e3838e532e71c8`
- `Linux 5.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.