{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-38000", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T04:51:23.976Z", "datePublished": "2025-06-06T13:03:35.405Z", "dateUpdated": "2026-08-05T11:58:51.349Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:58:51.349Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue()\n\nWhen enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the\nchild qdisc's peek() operation before incrementing sch->q.qlen and\nsch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may\ntrigger an immediate dequeue and potential packet drop. In such cases,\nqdisc_tree_reduce_backlog() is called, but the HFSC qdisc's qlen and backlog\nhave not yet been updated, leading to inconsistent queue accounting. This\ncan leave an empty HFSC class in the active list, causing further\nconsequences like use-after-free.\n\nThis patch fixes the bug by moving the increment of sch->q.qlen and\nsch->qstats.backlog before the call to the child qdisc's peek() operation.\nThis ensures that queue length and backlog are always accurate when packet\ndrops or dequeues are triggered during the peek." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Triggering requires configuring an HFSC qdisc with an RSC service curve and a peek-dequeueing child qdisc (netem/codel/fq_codel/tbf) via RTM_NEWQDISC/RTM_NEWTCLASS netlink, then transmitting a packet locally. Per kernel scoring guidance, tc/netlink qdisc configuration is a local attack vector.\nAC:L - The attacker fully controls both the qdisc hierarchy (hfsc + netem with an inner qdisc that rejects on enqueue) and the packet that drives hfsc_enqueue(), so the peek-time drop and the resulting qlen underflow are triggered deterministically with no race to win and no reliance on uncontrolled state.\nPR:L - Qdisc configuration is gated by netlink_net_capable(CAP_NET_ADMIN) against the netns owning user_ns, which any unprivileged user obtains via `unshare -Urn` and then applies to lo/dummy/veth inside the namespace. No real root in the init namespace is needed.\nUI:N - The attacker performs the qdisc setup and generates the triggering traffic entirely on their own; no victim action or interaction is required.\nS:U - The corruption is confined to kernel scheduler state in the same security authority; it is a standard local kernel privilege escalation with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The accounting inconsistency leaves a freed/empty hfsc_class linked in the eligible and vt-trees, and the commit explicitly states this leads to use-after-free; a UAF on a ~512-byte generic-kmalloc object with embedded rb_nodes yields a controlled read primitive over sprayed kernel objects.\nI:H - Dangling rb_node linkage of a freed hfsc_class means subsequent eltree/vttree insert, update, and rebalance operations write attacker-influenced values into reclaimed heap memory, giving a write primitive suitable for control-flow hijacking and privilege escalation.\nA:H - Even without full exploitation, the q.qlen/backlog underflow to 0xFFFFFFFF and the stale active-list entry cause use-after-free oopses, KASAN splats, and reported infinite loops in hfsc_dequeue(), crashing or hanging the machine." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_hfsc.c" ], "versions": [ { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "1034e3310752e8675e313f7271b348914008719a", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "f9f593e34d2fb67644372c8f7b033bdc622ad228", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "89c301e929a0db14ebd94b4d97764ce1d6981653", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "93c276942e75de0e5bc91576300d292e968f5a02", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "49b21795b8e5654a7df3d910a12e1060da4c04cf", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "3f3a22eebbc32b4fa8ce9c1d5f9db214b45b9335", "status": "affected", "versionType": "git" }, { "version": "12d0ad3be9c3854e52ec74bb83bb6f43612827c7", "lessThan": "3f981138109f63232a5fb7165938d4c945cc1b9d", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_hfsc.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.294", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.238", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.185", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.141", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.93", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.31", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14.9", "lessThanOrEqual": "6.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.15", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.4.294" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.10.238" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.185" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.141" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.31" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.14.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.15" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/1034e3310752e8675e313f7271b348914008719a" }, { "url": "https://git.kernel.org/stable/c/f9f593e34d2fb67644372c8f7b033bdc622ad228" }, { "url": "https://git.kernel.org/stable/c/89c301e929a0db14ebd94b4d97764ce1d6981653" }, { "url": "https://git.kernel.org/stable/c/f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4" }, { "url": "https://git.kernel.org/stable/c/93c276942e75de0e5bc91576300d292e968f5a02" }, { "url": "https://git.kernel.org/stable/c/49b21795b8e5654a7df3d910a12e1060da4c04cf" }, { "url": "https://git.kernel.org/stable/c/3f3a22eebbc32b4fa8ce9c1d5f9db214b45b9335" }, { "url": "https://git.kernel.org/stable/c/3f981138109f63232a5fb7165938d4c945cc1b9d" } ], "title": "sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html" }, { "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T17:32:58.709Z" } } ] } }