DF-0370

Marker PDU reflection without rate-limiting or request-address validation: on-link amplification DoS

Summary

lacp_marker_input(:1911-1922) unconditionally converts MARKER_TYPE_INFO to RESPONSE and re-enqueues via lagg_enqueue. Unlike lacp_sm_tx(rate-limited by ppsratecheck :1829) marker responses have NO rate limiting. Slow-protocols multicast dst(:1901) delivers to every LAGG on segment -> N amplified responses per injected frame. No validation that mi_rq_system matches local. On-link attacker sustains bandwidth/CPU exhaustion.

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Severity: Low
Status: new
Bucket: Base system — network stack
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
CWE: CWE-770
File: sys/net/lagg/ieee8023ad_lacp.c
Lines: 1911-1922
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 04:51:42
Attempts: 1
Runtime: —
Code hash: 3caa0366234eff64
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 04:51:42
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-0370/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0370 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	736 B	↓ raw
fix.diff	suggested-fix	fix for amplification bug	433 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0370 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: amplification

Impact: none

Source file: sys/net/lagg/ieee8023ad_lacp.c

Mechanism

CONFIRMED: lacp_marker_input unconditionally converts MARKER_TYPE_INFO to RESPONSE and re-enqueues. No rate limiting unlike lacp_sm_tx. Amplification vector.

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/lagg/ieee8023ad_lacp.c:1911.

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/lagg/ieee8023ad_lacp.c:1911. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0370. No PoC binary (source-only verification).

Verified recommended fix

Document missing rate limiting (requires struct field addition for full fix). Supersedes finding proposal.

Verdict

CONFIRMED source-only: marker responses have no rate limiting. Amplification vector.