DF-0316

OOB read: wg_output dereferences 4 bytes from mbuf without length check in BPF AF_UNSPEC path

Summary

wg_output(:2289) *(mtod(m,uint32_t*)) reads AF without checking m_pkthdr.len>=4. BPF DLT_NULL write of 0-3 bytes -> reads stale mbuf data. m_adj(m,4) on <4 byte packet -> m_len underflow. Root-only via /dev/bpf.

Discussion (0)

No comments yet.

Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:L
CWE: CWE-125
File: sys/net/wg/if_wg.c
Lines: 2289-2290
Area: net
Discovered: 2026-06-30
Updated: 2026-06-30

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 01:06:54
Attempts: 1
Runtime: —
Code hash: 50b572366f36f6ec
Guest: DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026
Build cmd: (combined) make -j6 nativekernel KERNCONF=X86_64_GENERIC
Run cmd: source-only; inspect sys/net/wg/if_wg.c:2289

jump to evidence pack ↓

Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 01:06:54
Runtime: —
Kernel: DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)
fix.diff: findings/poc/DF-0316/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-0316 · 5 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for DF-0316	412 B	view raw
VERDICT.md	verdict	source-confirmation + fix summary	562 B	↓ raw
build.sh	build-log	combined-build validation note	333 B	view raw
run.sh	run-log	source-only (no runtime PoC)	127 B	view raw
env.txt	environment	guest uname + build env	218 B	view raw

VERDICT.md verdict source-confirmation + fix summary

↓ download raw

DF-0316 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: wg_output reads (mtod(m,uint32_t)) (the AF) without checking m_pkthdr.len>=4, then m_adj(m,4) on a <4-byte packet underflows m_len. Root-only via /dev/bpf DLT_NULL.

Impact ceiling

none

Cited refs

sys/net/wg/if_wg.c:2289

Fix

Reject packets shorter than sizeof(uint32_t) before reading the AF / m_adj.

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/net/wg/if_wg.c:2289 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0

↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/net/wg/if_wg.c:2289; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0316/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Reject packets shorter than sizeof(uint32_t) before reading the AF / m_adj. Full diff: findings/poc/DF-0316/fix.diff.

Verdict

REAL: wg_output reads (mtod(m,uint32_t)) (the AF) without checking m_pkthdr.len>=4, then m_adj(m,4) on a <4-byte packet underflows m_len. Root-only via /dev/bpf DLT_NULL.