{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-37798",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-37798"
  ],
  "published": "2025-05-02T14:16:22Z",
  "summary": "codel: remove sch->q.qlen check before qdisc_tree_reduce_backlog()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncodel: remove sch->q.qlen check before qdisc_tree_reduce_backlog()\n\nAfter making all ->qlen_notify() callbacks idempotent, now it is safe to\nremove the check of qlen!=0 from both fq_codel_dequeue() and\ncodel_qdisc_dequeue().",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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      "database_specific": {
        "per_version": {
          "1:6.12.19-1+rpt1~bpo12+1": {
            "linux_commit": "121c2c384b9c2f4790ffb31b2cd25c7d75c8fda0",
            "upstream_version": "6.12.19",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.24"
          },
          "1:6.12.19-1+rpt1": {
            "linux_commit": "121c2c384b9c2f4790ffb31b2cd25c7d75c8fda0",
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            "assessment": "commit ancestry (strak rule)",
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            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.24"
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    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-37798"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7a742a9506849d1c1aa71e36c89855ceddc7d58e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cc71a757da78dd4aa1b4a9b19cb011833730ccf2"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/829c49b6b2ff45b043739168fd1245e4e1a91a30"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2f9761a94bae33d26e6a81b31b36e7d776d93dc1"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/4d55144b12e742404bb3f8fee6038bafbf45619d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e73c838c80dccb9e4f19becc11d9f3cb4a27d483"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/342debc12183b51773b3345ba267e9263bdfaaef"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable state is created and triggered through tc/rtnetlink qdisc configuration (RTM_NEWQDISC/RTM_NEWTCLASS/RTM_DELTCLASS) plus locally generated traffic over a loopback or veth device. There is no remote entry point into the qdisc class hierarchy setup.\nAC:L - The attacker controls every input: the qdisc hierarchy, CoDel's target/interval (unvalidated in codel_change()), the device MTU that defeats the backlog>mtu drop guard, the traffic that fills and empties the queue, and the moment the class is deleted. The inconsistent active-but-empty class state persists indefinitely, so no race window must be won.\nPR:L - Configuring qdiscs requires CAP_NET_ADMIN, but rtnetlink checks it via sk_ns_capable(sk, net->user_ns, CAP_NET_ADMIN), which any unprivileged local user obtains inside a `unshare -Urn` user+network namespace. Per kernel scoring guidance, tc/qdisc reachable through user namespaces is Low, not High.\nUI:N - The attacker performs every step \u2014 qdisc setup, traffic generation, and class deletion \u2014 within their own namespace. No victim action or interaction is needed.\nS:U - The corruption is confined to kernel heap objects and scheduler data structures managed by the same kernel security authority. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed drr_class/qfq_class/hfsc_class remains linked in the parent's active list and rbtrees; after heap reclaim the attacker controls the object contents and the traversals read kernel pointers back out of it, yielding an arbitrary-read primitive and kernel address disclosure. Per guidance, use-after-free is High.\nI:H - Subsequent list_del/list_add and rb_erase operations write through pointers stored in the freed object, and drr_dequeue()/agg_dequeue() perform an indirect call via cl->qdisc->ops->peek() on reclaimed memory, giving a write primitive and control-flow hijack suitable for full privilege escalation.\nA:H - Even without successful exploitation, the dangling class in the active list/rbtree causes list and red-black-tree corruption and dereference of poisoned or freed pointers, producing a kernel oops or panic that can be triggered repeatedly by an unprivileged user."
    }
  }
}