DF-0425

MRT6 setsockopt handlers cast mtod() without verifying m_len against struct size: reads uninitialized mbuf data

Summary

ip6_mrouter_set(:277-309): only MRT6_INIT validates m_len(:426). ADD_MIF/DEL_MIF/ADD_MFC/DEL_MFC/PIM all mtod(m,struct X*) and deref fields with no m_len check. Too-short buffer reads bytes past m_len but inside mbuf data area — uninitialized kernel heap/stack. Garbage values drive control flow: mifi/flags/parent/pim int. Error-code oracle for privileged user; can install mif/mfc entries partially from kernel memory.

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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:H/UI:N/S:U/C:L/I:N/A:N
CWE: CWE-457
File: sys/netinet6/ip6_mroute.c
Lines: 277-309
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: leak
Confidence: likely
Tested: 2026-07-23 04:51:46
Attempts: 1
Runtime: —
Code hash: 2ffe07247e081f41
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 04:51:46
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-0425/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0425 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	710 B	↓ raw
fix.diff	suggested-fix	fix for oob-read bug	452 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0425 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: oob-read

Impact: leak

Source file: sys/netinet6/ip6_mroute.c

Mechanism

CONFIRMED: ADD_MIF/DEL_MIF/ADD_MFC/DEL_MFC/PIM all mtod and deref fields with no m_len check. Too-short buffer reads uninitialized mbuf data.

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/netinet6/ip6_mroute.c:277.

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/netinet6/ip6_mroute.c:277. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0425. No PoC binary (source-only verification).

Verified recommended fix

Add m_len checks for ADD_MIF and other MRT6 commands. Matches finding proposal.

Verdict

CONFIRMED source-only: MRT6 commands mtod/deref without m_len check. Reads uninitialized mbuf.