{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-37797", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T04:51:23.941Z", "datePublished": "2025-05-02T14:16:01.905Z", "dateUpdated": "2026-08-05T11:57:36.042Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:57:36.042Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: hfsc: Fix a UAF vulnerability in class handling\n\nThis patch fixes a Use-After-Free vulnerability in the HFSC qdisc class\nhandling. The issue occurs due to a time-of-check/time-of-use condition\nin hfsc_change_class() when working with certain child qdiscs like netem\nor codel.\n\nThe vulnerability works as follows:\n1. hfsc_change_class() checks if a class has packets (q.qlen != 0)\n2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g.,\n codel, netem) might drop packets and empty the queue\n3. The code continues assuming the queue is still non-empty, adding\n the class to vttree\n4. This breaks HFSC scheduler assumptions that only non-empty classes\n are in vttree\n5. Later, when the class is destroyed, this can lead to a Use-After-Free\n\nThe fix adds a second queue length check after qdisc_peek_len() to verify\nthe queue wasn't emptied." } ], "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 - The entire attack sequence (create hfsc qdisc, attach a codel/netem child, `tc class change`, then `tc class del`) is driven through rtnetlink RTM_NEWTCLASS/RTM_DELTCLASS messages, which require local system access. Per kernel CNA guidance, tc/netlink qdisc bugs are Local.\nAC:L - This is a deterministic time-of-check/time-of-use flaw inside a single netlink operation, not a thread race — the attacker picks the child qdisc (codel/netem) and its parameters so the peek is guaranteed to drop the packet and empty the queue. No condition outside the attacker's control is involved, and a reliable reproducer existed.\nPR:L - The tc class paths only check `netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN)`, which an unprivileged user satisfies inside a new user+net namespace (`unshare -Urn`), where they can create a dummy/veth device, build the hfsc hierarchy and generate the traffic. Per guidance, tc/qdisc reachable via user namespaces is Low, not High.\nUI:N - The attacker performs every step — qdisc/class configuration, packet generation, class change and class deletion — with no action by any other user. Subsequent dequeue on the attacker's own device triggers the freed-object access.\nS:U - The corruption and its consequences are confined to the kernel's own memory and privilege domain; there is no crossing of a VM, IOMMU, or other security-authority boundary. Standard kernel-local privilege escalation is Unchanged.\nC:H - The freed `hfsc_class` remains linked in the parent's vt_tree/eltree, so `vttree_firstfit()`/`eltree_get_mindl()` read `cl_f`, `cl_vt`, `cl_parent` and `cl->qdisc` out of reclaimed slab memory, giving an attacker who sprays the slot a controlled read primitive and kernel memory disclosure.\nI:H - The dangling rb_node yields `rb_erase()`/`rb_insert_color()` pointer writes plus the direct `cl->cl_parent->cl_cvtmin = cl->cl_vt` write through freed memory, and `qdisc_dequeue_peeked()` makes an indirect call through `cl->qdisc->ops->dequeue` read from the freed object — a full write/control-flow-hijack primitive for privilege escalation.\nA:H - Even without successful exploitation, traversing and erasing rb-tree nodes inside a kfree()d `hfsc_class` reliably corrupts the scheduler tree and panics or oopses the kernel, and the attacker can repeat it at will." } ] } ], "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": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "28b09a067831f7317c3841812276022d6c940677", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "39b9095dd3b55d9b2743df038c32138efa34a9de", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "fcc8ede663569c704fb00a702973bd6c00373283", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "20d584a33e480ae80d105f43e0e7b56784da41b9", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "3aa852e3605000d5c47035c3fc3a986d14ccfa9f", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "86cd4641c713455a4f1c8e54c370c598c2b1cee0", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "bb583c88d23b72d8d16453d24856c99bd93dadf5", "status": "affected", "versionType": "git" }, { "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14", "lessThan": "3df275ef0a6ae181e8428a6589ef5d5231e58b5c", "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": "4.14", "status": "affected" }, { "version": "0", "lessThan": "4.14", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.293", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.237", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.181", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.136", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.89", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.26", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14.5", "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": "4.14", "versionEndExcluding": "5.4.293" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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"url": "https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677" }, { "url": "https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de" }, { "url": "https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283" }, { "url": "https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9" }, { "url": "https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f" }, { "url": "https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0" }, { "url": "https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5" }, { "url": "https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c" } ], "title": "net_sched: hfsc: Fix a UAF vulnerability in class handling", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html" }, { "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T19:55:28.428Z" } }, { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2025-37797", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-06-10T20:40:32.363946Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-06-11T18:44:02.667Z" } } ] } }