245 lines
12 KiB
JSON
245 lines
12 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2024-40920",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2024-07-12T12:17:45.582Z",
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"datePublished": "2024-07-12T12:25:02.222Z",
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"dateUpdated": "2026-08-05T11:34:00.976Z"
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},
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"containers": {
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"cna": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T11:34:00.976Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mst: fix suspicious rcu usage in br_mst_set_state\n\nI converted br_mst_set_state to RCU to avoid a vlan use-after-free\nbut forgot to change the vlan group dereference helper. Switch to vlan\ngroup RCU deref helper to fix the suspicious rcu usage warning."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
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"baseScore": 7.1,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:A - The buggy dereference is reached from the STP BPDU receive path (`br_stp_rcv` → `br_port_state_selection` → `br_set_state` → `br_mst_set_state`), so an attacker on the same L2 segment can drive port state transitions into it; STP BPDUs use the link-local `01:80:C2:00:00:00` LLC group address and are not routable, so this is adjacent rather than network.\nAC:L - On an MST-enabled bridge running kernel STP the unannotated dereference is hit deterministically on every port state transition, and the attacker drives both sides — flapping BPDUs force repeated transitions while port add/remove concurrently republishes `p->vlgrp` — with no timing window or memory layout that must be won.\nPR:N - STP BPDU processing in `br_stp_rcv()` has no authentication whatsoever — a frame from the segment is accepted on any non-disabled, non-BPDU-guarded port — so the adjacent attacker needs no credentials on the target host.\nUI:N - Port state transitions occur automatically from received BPDUs and from the forward-delay timer; no administrator or user action is needed once the bridge is in MST mode.\nS:U - The faulty dereference, the resulting fault, and the log disclosure are all confined to the kernel that owns the bridge; no VM, IOMMU, or sandbox boundary is crossed.\nC:L - The `lockdep_rcu_suspicious()` report dumps a full kernel backtrace with raw stack and register addresses (as seen in the syzbot trace) into the kernel log, disclosing text and stack layout useful for defeating KASLR; there is no bulk or arbitrary memory read.\nI:N - The defect is a read-side annotation mismatch — no attacker-controlled data is written and no out-of-bounds or freed memory is modified, so no write or control-flow-hijack primitive results.\nA:H - Without the RCU dereference the load of `p->vlgrp` carries no `READ_ONCE()` or dependency ordering, so a softirq reader racing a concurrent `nbp_vlan_flush()`/`nbp_vlan_init()` can traverse `vg->vlan_list` and write `vg->pvid_state` on a NULL or not-yet-published group, oopsing the kernel and taking down the bridging host."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"net/bridge/br_mst.c"
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],
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}
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"title": "net: bridge: mst: fix suspicious rcu usage in br_mst_set_state",
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"id": "CVE-2024-40920",
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"role": "CISA Coordinator",
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"options": [
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{
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"title": "CISA ADP Vulnrichment",
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