CVE-2026-64084: hwmon: (pmbus/adm1266) cap PDIO scan in get_multiple at ADM1266_PDIO_NR
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (pmbus/adm1266) cap PDIO scan in get_multiple at ADM1266_PDIO_NR
adm1266_gpio_get_multiple() iterates the PDIO portion of the
caller-supplied mask using
for_each_set_bit_from(gpio_nr, mask,
ADM1266_GPIO_NR + ADM1266_PDIO_STATUS) {
...
}
where ADM1266_PDIO_STATUS is the PMBus command code (0xE9, i.e. 233),
not the number of PDIO pins. The intended upper bound is
ADM1266_GPIO_NR + ADM1266_PDIO_NR = 25.
gpiolib hands in a mask sized for gc.ngpio (= 25 bits on this chip),
so the iteration walks find_next_bit() up to 242, reading up to 217
extra bits (a handful of unsigned-long words: four on 64-bit, seven
on 32-bit) of whatever lives past the end of the mask in the
caller's stack. Any incidental set bit in that range then drives a
set_bit(gpio_nr, bits) call that writes past the end of the
caller-supplied bits array too -- both out-of-bounds.
Substitute ADM1266_PDIO_NR for the constant so the scan stops at the
last real PDIO bit.
Security readout for executives and security teams
Plain-English summary
CVE-2026-64084 is a Linux kernel bug in the ADM1266 PMBus hardware-monitoring GPIO driver. A local user could trigger out-of-bounds memory reads and writes through normal kernel GPIO handling, potentially causing data exposure, corruption, or system compromise on systems using this driver.
Executive priority
High priority for specialized Linux fleets, especially embedded, appliance, lab, or infrastructure systems using ADM1266 hardware monitoring. Broader enterprise exposure may be narrow, but kernel memory corruption with local low-privilege access warrants prompt validation and patch tracking.
Technical view
adm1266_gpio_get_multiple() scans PDIO bits using ADM1266_PDIO_STATUS, a PMBus command value, instead of ADM1266_PDIO_NR. The loop can read beyond a 25-bit mask and write beyond the caller-supplied bits array when incidental stack bits are set. The kernel fix caps scanning at the real PDIO count.
Likely exposure
Exposure is likely limited to Linux systems with the ADM1266 PMBus hardware-monitoring GPIO path present and reachable. The bundle lists Linux as affected across several version entries, but downstream distro kernels may have backports, so version-only checks are insufficient.
Exploitation context
The CVSS vector is local, low-complexity, low-privilege, and no user interaction. The source bundle marks KEV as false, and no supplied source states active exploitation. Treat this as a local privilege and kernel memory-corruption risk until vendor status is confirmed.
Researcher notes
The key defect is an incorrect loop bound: ADM1266_PDIO_STATUS is 0xE9, while the actual PDIO count is 16 and total GPIO count is 25. The source describes both out-of-bounds reads from the mask and out-of-bounds writes to the bits array.
Mitigation direction
Update to a kernel or distro package containing the referenced stable fix.
Check vendor advisories for backported fixes before relying on upstream version numbers.
Prioritize systems exposing ADM1266 PMBus or related GPIO functionality.
Reduce unnecessary local user access on affected systems.
If no patch is available, follow vendor guidance for driver-specific risk reduction.
Validation and detection
Inventory Linux kernels and identify systems using the adm1266 driver.
Confirm whether installed kernel packages include one of the listed stable commits or vendor backports.
Review hardware profiles for ADM1266 PMBus devices or matching platform support.
Track remediation through package version, kernel changelog, or commit evidence.
Verify no affected assets remain after maintenance windows.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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1CVSS vectors
3Timeline events
0ADP providers
9Source links
CVSS vector scores
1 official score
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