DF-0421

ng_ubt_rcvdata calls panic() on malformed HCI frames from netgraph hook: local DoS

Summary

ng_ubt_rcvdata(:1755-1775) calls panic() on: (1) mbuf<4 bytes(:1755-1757), (2) HCI cmd payload>UBT_CTRL_BUFFER_SIZE(:1762-1765), (3) ACL payload>UBT_BULK_WRITE_BUFFER_SIZE(:1772-1775). panic() halts kernel. Privileged netgraph user or buggy upper-layer node sends single malformed mbuf -> system crash. Should drop packet + return EMSGSIZE.

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Severity: Low
Status: new
Bucket: Base system — network stack
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-617
File: sys/netgraph7/bluetooth/drivers/ubt/ng_ubt.c
Lines: 1755-1775
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: dos
Confidence: certain
Tested: 2026-07-23 04:51:46
Attempts: 1
Runtime: —
Code hash: 4ce76066358f1bcc
Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 x86_64
Build cmd: n/a (source-only verification)
Run cmd: n/a (source-only verification)

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 04:51:46
Runtime: —
Kernel: 6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)
fix.diff: findings/poc/DF-0421/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0421 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	751 B	↓ raw
fix.diff	suggested-fix	fix for dos bug	1.2 KB	view raw

VERDICT.md verdict source verification verdict

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DF-0421 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: dos

Impact: dos

Source file: sys/netgraph7/bluetooth/drivers/ubt/ng_ubt.c

Mechanism

CONFIRMED: ng_ubt_rcvdata calls panic() on bad HCI frame sizes instead of error return. Kernel halt from privileged netgraph user. Fix: replace panic with m_freem+break.

Fix

See fix.diff for the git-apply-able patch.

Build validation

Combined kernel build with all 70 Low-severity fixes: rc=0, -Werror. All fixes compile cleanly in X86_64_GENERIC kernel configuration.

Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff compiles cleanly in combined kernel build (rc=0, -Werror). Source trace confirms bug at sys/netgraph7/bluetooth/drivers/ubt/ng_ubt.c:1755.

Combined build: 70 fix.diffs applied to /usr/src, nativekernel KERNCONF=X86_64_GENERIC rc=0 -Werror. All fixes compile.

↓ fix.diff6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)

Confirmed kernel references

Detail

Exploit chain

none (non-corruption Low severity finding; source-only confirmation)

Evidence (decisive lines)

Source-traced at sys/netgraph7/bluetooth/drivers/ubt/ng_ubt.c:1755. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0421. No PoC binary (source-only verification).

Verified recommended fix

Replace panic() with m_freem+break. Matches finding proposal.

Verdict

CONFIRMED source-only: ng_ubt_rcvdata calls panic() on bad frame sizes. Kernel halt.