# CVE-2026-89587

## Summary

- **CVE ID:** CVE-2026-89587
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 14, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:

ACPI: pfr_update: fix stack buffer overflow in query_capability()

query_capability() copies four ACPI buffer objects returned by the
firmware _DSM into fixed-size u8[16] fields in struct
pfru_update_cap_info using memcpy with the firmware-supplied length:

  memcpy(&cap_hdr->code_type,
         elements[CAP_CODE_TYPE_IDX].buffer.pointer,
         elements[CAP_CODE_TYPE_IDX].buffer.length);

The same pattern repeats for drv_type, platform_id, and oem_id.
If the firmware returns buffer.length > 16 for any of these fields,
memcpy writes past the destination array.

struct pfru_update_cap_info is stack-allocated in pfru_ioctl().

Confirmed with KASAN on 7.2-rc6: three stack-out-of-bounds reports
are generated when a DSM returns 64-byte buffers, with writes reaching
44 bytes past the end of cap_hdr's [64, 156) frame window into
adjacent stack redzones.

Introduce a helper pointer to out_obj->package.elements and use it
to validate each buffer length against its destination field size
before copying, returning -EINVAL if the firmware supplies an
oversized buffer.

## Affected Products

- Linux — Linux (0db89fa243e5edc5de38c88b369e4c3755c5fb74)
- Linux — Linux (5.17)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/a2151624b55029dad0ca7efd17fb83a0461c8843)
- [CNA](https://git.kernel.org/stable/c/6d4ed2fd022bc862b156e53aae163b61259e1caa)
- [CNA](https://git.kernel.org/stable/c/15d2b7f38f95d28652170344f39ee492c55e567c)
- [CNA](https://git.kernel.org/stable/c/ced45be0073a8a31b30b4a7f68cd3a15734515de)
- [CNA](https://git.kernel.org/stable/c/d3af83e327565a9444cebc0db714cb837e493046)
- [CNA](https://git.kernel.org/stable/c/c5a31b4e7e37c92550be9a2edf51ca853a4d251a)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.14%
- **EPSS Percentile:** 3.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._