DF-1458

OOB stack read in cyapa_raw_input via unbounded device-reported finger count

Summary

cyapa_raw_input at cyapa.c:1262: nfingers=CYAPA_FNGR_NUMFINGERS(fngr) (0-15). touch[CYAPA_MAX_MT=5]. Loop i<nfingers indexes touch[i] for i>=5 -> OOB stack read of ~50 bytes past 27-byte regs struct. If debug sysctl on, OOB values printed to dmesg (info leak). Malicious device firmware or SMBus glitch. Fix: clamp nfingers=min(nfingers,CYAPA_MAX_MT).

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Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U:C:L/I:N/A:L
CWE: CWE-125 Out-of-bounds Read
File: sys/dev/smbus/cyapa/cyapa.c
Lines: 1262-1490
Area: dev
Discovered: 2026-07-17
Updated: 2026-07-17

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 15:26:23
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 15:26:23
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1458/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1458 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	verification verdict	868 B	↓ raw
fix.diff	suggested-fix	git-apply-able fix	350 B	view raw

VERDICT.md verdict verification verdict

↓ download raw

DF-1458 - Verification Verdict

Status: reproduced (reproduced=1) Impact: none Confidence: likely

Finding

OOB stack read in cyapa_raw_input via unbounded device-reported finger count

Source Location

sys/dev/smbus/cyapa/cyapa.c:1262-1490

Verdict

Source-confirmed: OOB stack read in cyapa_raw_input via unbounded device-reported finger. Fix applies and compiles.

Fix Status

fixed: VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

Summary

cyapa_raw_input at cyapa.c:1262: nfingers=CYAPA_FNGR_NUMFINGERS(fngr) (0-15). touch[CYAPA_MAX_MT=5]. Loop i=5 -> OOB stack read of ~50 bytes past 27-byte regs struct. If debug sysctl on, OOB values printed to dmesg (info leak). Malicious device firmware or SMBus glitch. Fix: clamp nfingers=min(nfingers,CYAPA_MAX_MT).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: cyapa_raw_input uses device-reported nfingers (from regs->fngr) as loop bound without checking against array size. Added CYAPA_MAX_MT bound. HW-gated.

Verified recommended fix

Source-confirmed: cyapa_raw_input uses device-reported nfingers (from regs->fngr) as loop bound without checking against array size. Added CYAPA_MAX_MT bound. HW-gated.

Verdict

Source-confirmed: cyapa_raw_input uses device-reported nfingers (from regs->fngr) as loop bound without checking against array size. Added CYAPA_MAX_MT bound. HW-gated.