Bug 2555107 (CVE-2026-98728)

Summary: CVE-2026-98728 kernel: tpm: fix off-by-four bounds check in tpm2_get_random()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Trusted Platform Module (TPM) driver. This flaw can lead to information disclosure when the kernel requests random data. Due to an incorrect bounds check when processing session-tagged responses, a truncated response can pass validation and cause the kernel to read past the end of the buffer. Consequently, stale kernel memory contents may be returned to the caller instead of random data, potentially exposing sensitive information.
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Description OSIDB Bzimport 2026-10-18 15:54:49 UTC 
In the Linux kernel, the following vulnerability has been resolved:

tpm: fix off-by-four bounds check in tpm2_get_random()

When the response carries the TPM2_ST_SESSIONS tag, tpm2_get_random()
skips the 4-byte parameter size field before locating the random data,
but the bounds check still validates the response length against
TPM_HEADER_SIZE.  A truncated response can pass the check and make
memcpy() read up to 4 bytes past the response end, so stale buffer
contents end up in the caller's random bytes.

Fix this by checking the response length against 'offset', which
already includes the skipped parameter size field.
Comment 1 Mauro Matteo Cascella 2026-10-22 23:40:11 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98728.mbox