CVE-2026-89436
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, the panasonic-laptop driver has an out-of-bounds write past the pcc->sinf[] array. The function acpi_pcc_retrieve_biosdata() writes a sentinel value at index equal to the SINF package count, which when num_sifr equals that count results in a one-element overflow (a silent 4-byte heap overflow). This occurs on hardware where HKEY.SQTY returns 37 and HKEY.SINF()'s package has 38 elements.
Risk Assessment
A local attacker or system fault could exploit the silent heap overflow in the kernel, leading to memory corruption, system instability, or potential privilege escalation. The vulnerability affects only specific Panasonic hardware with a faulty DSDT.
Recommendation
Update the Linux kernel to a version containing the fix that skips the sentinel write when there is no room for it in the pcc->sinf[] array. If updating is not possible, consider restricting access to the affected hardware or monitoring for instability.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: platform/x86: panasonic-laptop: Fix sentinel write past pcc->sinf[] acpi_pcc_retrieve_biosdata() rejects SINF packages only when pcc->num_sifr is strictly less than hkey->package.count, then unconditionally writes a trailing sentinel at pcc->sinf[hkey->package.count]. But pcc->sinf[] is allocated with exactly pcc->num_sifr elements (valid indices 0..num_sifr-1), so that write needs num_sifr strictly greater than package.count to stay in bounds -- num_sifr == package.count passes the existing check but still overflows by one element. This is exactly the case probe()'s existing num_sifr++ workaround ("Some DSDT-s have an off-by-one bug where the SINF package count is one higher than the SQTY reported value") is written to accommodate: when a DSDT's SINF package count equals SQTY+1, the workaround makes num_sifr equal to package.count, which is precisely the boundary that overflows here. Found via UBSan (array-index-out-of-bounds) on hardware where HKEY.SQTY returns 37 and HKEY.SINF()'s package has 38 elements: num_sifr becomes 38 after the += 1 workaround, the loop correctly fills indices 0..37, and the sentinel write then targets index 38, one past the end -- a silent 4-byte heap overflow on kernels without CONFIG_UBSAN. Tightening the rejection check to num_sifr <= package.count would avoid the overflow but breaks probe() entirely on exactly this hardware, since num_sifr == package.count is the case the off-by-one workaround exists to support. Nothing else in the driver reads this sentinel value back, so simply skip the write when there is no room for it instead.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS