DF-0553

SIOCSETVLAN accepts reserved VLAN IDs (0 and 0xFFF) without validation

Summary

SIOCSETVLAN handler(:996-1007): copies struct vlanreq, calls vlan_config(ifv,vlr.vlr_parent,vlr.vlr_tag) no validation of vlr_tag. IEEE 802.1Q reserves VID 0(priority-tagged) and VID 0xFFF(valid range 1-4094). Privileged user can configure reserved IDs. Operational/protocol correctness issue. Fix: if(vlr_tag==0||(vlr_tag&0xfff)==0xfff) return EINVAL.

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Severity: Info
Status: new
Bucket: Base system — network stack
Confidence: likely
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:N/A:N
CWE: CWE-20
File: sys/net/vlan/if_vlan.c
Lines: 996-1007
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 18:17:16
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 18:17:16
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-0553/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0553 · 1 files

File	Type	Description	Size
manifest.json	file		387 B	view raw

Fix verification

not_testable

baseline reproduced→ patch + rebuild →patched clean

recommended fix identified; fix.diff not authored/validated in this batch

recommended fix identified; fix.diff not authored/validated in this batch

combined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Info severity)

Evidence (decisive lines)

Source-confirmed at sys/net/vlan/if_vlan.c:996: SIOCSETVLAN accepts reserved VLAN IDs (0 and 0xFFF)

Verified recommended fix

Source-confirmed at sys/net/vlan/if_vlan.c:996: SIOCSETVLAN accepts reserved VLAN IDs (0 and 0xFFF)

Verdict

Source-confirmed at sys/net/vlan/if_vlan.c:996: SIOCSETVLAN accepts reserved VLAN IDs (0 and 0xFFF)