CVE-2026-72135
Received
Received - Intake
Heap Buffer Overflow in Linux Kernel TPM Driver
Vulnerability report for CVE-2026-72135, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-08-15
Last updated on: 2026-08-15
Assigner: kernel.org
Description
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | From 6.12 (inc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
