CVE-2025-37953

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htb_deactivate()\n\nFor htb_next_rb_node(), after calling the 1st htb_deactivate(), the\nclprio[prio]->ptr could be already set to NULL, which means\nhtb_next_rb_node() is vulnerable here.\n\nFor htb_deactivate(), although we checked qlen before calling it, in\ncase of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again\nwhich triggers the warning inside.\n\nTo fix the issues here, we need to:\n\n1) Make htb_deactivate() idempotent, that is, simply return if we\n already call it before.\n2) Make htb_next_rb_node() safe against ptr==NULL.\n\nMany thanks to Alan for testing and for the reproducer."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/sch_htb.c"], "versions": [{"version": "e6b45f4de763b00dc1c55e685e2dd1aaf525d3c1", "lessThan": "99ff8a20fd61315bf9ae627440a5ff07d22ee153", "status": "affected", "versionType": "git"}, 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"https://git.kernel.org/stable/c/3769478610135e82b262640252d90f6efb05be71"}], "title": "sch_htb: make htb_deactivate() idempotent", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T19:57:42.885Z"}}]}}

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Alan inform\u00f3 una desreferencia de puntero NULL en htb_next_rb_node() despu\u00e9s de que htb_qlen_notify() fuera idempotente. Resulta que en el siguiente caso introdujo alguna regresi\u00f3n: htb_dequeue_tree(): |-> fq_codel_dequeue() |-> qdisc_tree_reduce_backlog() |-> htb_qlen_notify() |-> htb_deactivate() |-> htb_next_rb_node() |-> htb_deactivate() Para htb_next_rb_node(), despu\u00e9s de llamar al primer htb_deactivate(), el clprio[prio]->ptr podr\u00eda estar ya establecido en NULL, lo que significa que htb_next_rb_node() es vulnerable aqu\u00ed. Para htb_deactivate(), aunque verificamos qlen antes de llamarlo, en caso de qlen==0 despu\u00e9s de qdisc_tree_reduce_backlog(), podemos llamarlo nuevamente, lo que activa la advertencia interna. Para solucionar estos problemas, necesitamos: 1) Hacer que htb_deactivate() sea idempotente, es decir, que simplemente regrese si ya lo llamamos. 2) Hacer que htb_next_rb_node() sea seguro contra ptr==NULL. Muchas gracias a Alan por las pruebas y por el reproductor."}], "id": "CVE-2025-37953", "lastModified": "2026-06-17T09:15:45.963", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-05-20T16:15:33.483", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/31ff70ad39485698cf779f2078132d80b57f6c07"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3769478610135e82b262640252d90f6efb05be71"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/98cd7ed92753090a714f0802d4434314526fe61d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/99ff8a20fd61315bf9ae627440a5ff07d22ee153"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a9945f7cf1709adc5d2d31cb6cfc85627ce299a8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c2d25fddd867ce20a266806634eeeb5c30cb520c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c4792b9e38d2f61b07eac72f10909fa76130314b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-476"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: sch_htb: make htb_deactivate() idempotent", "id": "2367580", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2367580"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nsch_htb: make htb_deactivate() idempotent\nAlan reported a NULL pointer dereference in htb_next_rb_node()\nafter we made htb_qlen_notify() idempotent.\nIt turns out in the following case it introduced some regression:\nhtb_dequeue_tree():\n|-> fq_codel_dequeue()\n|-> qdisc_tree_reduce_backlog()\n|-> htb_qlen_notify()\n|-> htb_deactivate()\n|-> htb_next_rb_node()\n|-> htb_deactivate()\nFor htb_next_rb_node(), after calling the 1st htb_deactivate(), the\nclprio[prio]->ptr could be already set to NULL, which means\nhtb_next_rb_node() is vulnerable here.\nFor htb_deactivate(), although we checked qlen before calling it, in\ncase of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again\nwhich triggers the warning inside.\nTo fix the issues here, we need to:\n1) Make htb_deactivate() idempotent, that is, simply return if we\nalready call it before.\n2) Make htb_next_rb_node() safe against ptr==NULL.\nMany thanks to Alan for testing and for the reproducer."], "name": "CVE-2025-37953", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-05-20T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-37953\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-37953\nhttps://lore.kernel.org/linux-cve-announce/2025052001-CVE-2025-37953-d825@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-06-24T09:44:23.725046+00:00", "updated": "2025-06-24T09:44:23.725094+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}