DF-0400

rt_fixchange indexes mask bytes by key length without verifying mask size: latent OOB read

Summary

rt_fixchange(:1130-1165): mlen=rt_key(rt->rt_parent)->sa_len then iterates xmp[i],xm1[i] indexed by key length. Guard only checks mlen<=rt_key(rt0)->sa_len, NOT rt_mask->sa_len. If mask sa_len < key sa_len -> OOB read. Currently not triggerable (radix allocates masks key-sized). Latent if mask/key sizing invariant relaxes.

Discussion (0)

No comments yet.

Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: speculative
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
CWE: CWE-125
File: sys/net/route.c
Lines: 1130-1165
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 04:51:45
Attempts: 1
Runtime: —
Code hash: f66d6d956cb0ba0f
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)

jump to evidence pack ↓

Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 04:51:45
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-0400/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-0400 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	711 B	↓ raw
fix.diff	suggested-fix	fix for oob-read bug	431 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0400 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: oob-read

Impact: none

Source file: sys/net/route.c

Mechanism

CONFIRMED: rt_fixchange uses mlen from rt_key but indexes xmp[]=rt_mask. If mask shorter than key -> OOB read. Latent (radix allocates masks key-sized).

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/route.c:1155.

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/route.c:1155. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0400. No PoC binary (source-only verification).

Verified recommended fix

Check mlen<=rt_mask length. Matches finding proposal.

Verdict

CONFIRMED source-only: rt_fixchange indexes mask by key length. OOB if mask shorter. Latent.