DF-0478

Rule set field not validated: 1<<set with set>=32 is UB enabling rule-set bypass

Summary

Line :487: ctx->sets & (1 << f->set). 1 is int(32-bit), f->set is uint8_t(0-255). ip_fw struct comment says set 0..31(ip_fw3.h:266) but add_rule_dispatch copies set from user without validation. set>=32: 1<<set is UB. x86 HW masks shift to 5 bits (set&31): set=32 treated as set=0, set=33 as set=1. Rule silently checked against wrong set bit -> potential bypass of disabled rule-set. Fix: if(set>=32) return EINVAL in add_rule_dispatch.

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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:L/A:N
CWE: CWE-754
File: sys/net/ipfw3/ip_fw3.c
Lines: 487
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 04:51:49
Attempts: 1
Runtime: —
Code hash: 7911a62ab972b013
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: likely
Tested: 2026-07-23 04:51:49
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-0478/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0478 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	670 B	↓ raw
fix.diff	suggested-fix	fix for ub bug	341 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0478 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: ub

Impact: none

Source file: sys/net/ipfw3/ip_fw3.c

Mechanism

CONFIRMED: ctx->sets & (1 << f->set). f->set is uint8_t(0-255). set>=32: 1<set < 32.

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/net/ipfw3/ip_fw3.c:487.

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/net/ipfw3/ip_fw3.c:487. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0478. No PoC binary (source-only verification).

Verified recommended fix

Add f->set<32 guard before shift. Matches finding proposal.

Verdict

CONFIRMED source-only: ctx->sets & (1<set). set>=32 -> 1<<set is UB.