DF-1114

RSDP accepted without checksum or Length validation (firmware-integrity hardening gap)

Summary

sdt_rsdp_search at acpi_sdt.c:120-135 matches RSDP on 8-byte signature ONLY. Never validates ACPI 1.0 checksum (byte 9), ACPI 2.0 extended checksum (byte 32), or Length field (byte 20). sdt_probe at :108-116 reads rsdp->Revision and unconditionally accesses XsdtPhysicalAddress (offsets 24-31) for Revision>=2. A 20-byte ACPI 1.0 RSDP with Revision forged to 2 reads XsdtPhysicalAddress from bytes outside the RSDP struct - arbitrary adjacent firmware memory - used as root-table address. Boot-time only. Attacker: malicious/buggy firmware or loader hint. Combined with DF-1113 amplifies DoS surface. Fix: validate checksum and Length>=sizeof(ACPI_TABLE_RSDP) for Revision>=2.

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Severity: Low
Status: new
Bucket: Base system — bus / platform / cpu
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U:C:N/I:L/A:L
CWE: CWE-345 Insufficient Verification of Data Authenticity
File: sys/platform/pc64/acpica/acpi_sdt.c
Lines: 120-114
Area: hw
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: dos
Confidence: certain
Tested: 2026-07-25 10:25:03
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: certain
Tested: 2026-07-25 10:25:03
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1114/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1114 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1114	653 B	↓ raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1114

↓ download raw

DF-1114 Verification Verdict

Severity: Low Impact class: dos Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: RSDP checksum validation (complex multi-line; documented, not applied)

Fix identified but complex multi-line change not applied to batch kernel build.

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): sdt_rsdp_search matches RSDP on 8-byte signature only; never validates ACPI checksums or Length field. Malformed RSDP feeds unchecked Length into mapping -> panic possible.

Verified recommended fix

REPRODUCED (source-only): sdt_rsdp_search matches RSDP on 8-byte signature only; never validates ACPI checksums or Length field. Malformed RSDP feeds unchecked Length into mapping -> panic possible.

Verdict

REPRODUCED (source-only): sdt_rsdp_search matches RSDP on 8-byte signature only; never validates ACPI checksums or Length field. Malformed RSDP feeds unchecked Length into mapping -> panic possible.