{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2024-40920", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-07-12T12:17:45.582Z", "datePublished": "2024-07-12T12:25:02.222Z", "dateUpdated": "2026-08-05T11:34:00.976Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:34:00.976Z" }, "descriptions": [ { "lang": "en", "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/bridge/br_mst.c" ], "versions": [ { "version": "8ca9a750fc711911ef616ceb627d07357b04545e", "lessThan": "caaa2129784a04dcade0ea92c12e6ff90bbd23d8", "status": "affected", "versionType": "git" }, { "version": "4488617e5e995a09abe4d81add5fb165674edb59", "lessThan": "7caefa2771722e65496d85b62e1dc4442b7d1345", "status": "affected", "versionType": "git" }, { "version": "e43dd2b1ec746e105b7db5f9ad6ef14685a615a4", "lessThan": "406bfc04b01ee47e4c626f77ecc7d9f85135b166", "status": "affected", "versionType": "git" }, { "version": "3a7c1661ae1383364cd6092d851f5e5da64d476b", "lessThan": "546ceb1dfdac866648ec959cbc71d9525bd73462", "status": "affected", "versionType": "git" }, { "version": "a2b01e65d9ba8af2bb086d3b7288ca53a07249ac", "status": "affected", "versionType": "git" }, { "version": "6.8.12", "lessThan": "6.9", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/bridge/br_mst.c" ], "versions": [ { "version": "6.1.93", "lessThan": "6.1.95", "status": "affected", "versionType": "semver" }, { "version": "6.6.33", "lessThan": "6.6.35", "status": "affected", "versionType": "semver" }, { "version": "6.9.3", "lessThan": "6.9.6", "status": "affected", "versionType": "semver" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.93", "versionEndExcluding": "6.1.95" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.33", "versionEndExcluding": "6.6.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9.3", "versionEndExcluding": "6.9.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8.12" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/caaa2129784a04dcade0ea92c12e6ff90bbd23d8" }, { "url": "https://git.kernel.org/stable/c/7caefa2771722e65496d85b62e1dc4442b7d1345" }, { "url": "https://git.kernel.org/stable/c/406bfc04b01ee47e4c626f77ecc7d9f85135b166" }, { "url": "https://git.kernel.org/stable/c/546ceb1dfdac866648ec959cbc71d9525bd73462" } ], "title": "net: bridge: mst: fix suspicious rcu usage in br_mst_set_state", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/caaa2129784a04dcade0ea92c12e6ff90bbd23d8", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/7caefa2771722e65496d85b62e1dc4442b7d1345", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/406bfc04b01ee47e4c626f77ecc7d9f85135b166", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/546ceb1dfdac866648ec959cbc71d9525bd73462", "tags": [ "x_transferred" ] }, { "url": "https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T21:57:50.802Z" } }, { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2024-40920", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2024-09-10T17:05:33.673278Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-09-11T17:33:03.619Z" } } ] } }