FKIE_CVE-2026-72135
Vulnerability from fkie_nvd - Published: 2026-08-15 06:21 - Updated: 2026-08-17 06:18
Severity
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 |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"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",
"versions": [
{
"lessThan": "ed0ffc2c016629e40ba041ed0424a772d8b02e2c",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "232dcf908eb7eb9d8046a9597975caf44270966e",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "dda695fab5e21f923d29e8cb01df256468ddfbd1",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "9c513dabd4540f811585a2087f23069767a284da",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "21a13f932972bc9836f58c44fcd47c62abdecd95",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "947b773caaa548672184df025271b29bdc80b0f1",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
},
{
"lessThan": "f20d61c22bcaf172d6790b6500e3838e532e71c8",
"status": "affected",
"version": "9488585b21bef0df1217e510c7134905d1d376a7",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"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",
"versions": [
{
"status": "affected",
"version": "5.0"
},
{
"lessThan": "5.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"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"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"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."
}
],
"id": "CVE-2026-72135",
"lastModified": "2026-08-17T06:18:13.280",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-08-15T06:21:30.973",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/21a13f932972bc9836f58c44fcd47c62abdecd95"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/232dcf908eb7eb9d8046a9597975caf44270966e"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/947b773caaa548672184df025271b29bdc80b0f1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/9c513dabd4540f811585a2087f23069767a284da"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1ed"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/dda695fab5e21f923d29e8cb01df256468ddfbd1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ed0ffc2c016629e40ba041ed0424a772d8b02e2c"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/f20d61c22bcaf172d6790b6500e3838e532e71c8"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Loading…
Loading…