CVE-2026-72135 (GCVE-0-2026-72135)
Vulnerability from cvelistv5
Published
2026-08-15 05:53
Modified
2026-08-17 05:40
Severity ?
VLAI Severity ?
EPSS score ?
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 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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 Version: 9488585b21bef0df1217e510c7134905d1d376a7 |
||
{
"containers": {
"cna": {
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"product": "Linux",
"programFiles": [
"drivers/char/tpm/tpm-dev.c",
"drivers/char/tpm/tpmrm-dev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
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"drivers/char/tpm/tpmrm-dev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "5.0"
},
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "5.10.261",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.97",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"nodes": [
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}
],
"negate": false,
"operator": "OR"
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],
"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-\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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"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; corrupting adjacent heap structures can oops or panic the kernel during subsequent TPM operations."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:40:45.521Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
],
"title": "tpm: Make the TPM character devices non-seekable",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72135",
"datePublished": "2026-08-15T05:53:10.315Z",
"dateReserved": "2026-08-09T03:40:39.907Z",
"dateUpdated": "2026-08-17T05:40:45.521Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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