CVE-2025-37823 (GCVE-0-2025-37823)
Vulnerability from cvelistv5
Published
2025-05-08 06:26
Modified
2026-08-05 11:57
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too Similarly to the previous patch, we need to safe guard hfsc_dequeue() too. But for this one, we don't have a reliable reproducer.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too\n\nSimilarly to the previous patch, we need to safe guard hfsc_dequeue()\ntoo. But for this one, we don\u0027t have a reliable reproducer."
        }
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            "baseSeverity": "HIGH",
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              "value": "AV:L - Exploitation requires configuring an HFSC qdisc hierarchy with a netem/codel child and deleting a class via rtnetlink (RTM_NEWQDISC/RTM_NEWTCLASS/RTM_DELTCLASS), which is a local netlink socket operation. Per kernel scoring guidance, tc/netlink qdisc bugs are Local.\nAC:L - The attacker deterministically controls every element: the HFSC class curves (HFSC_RSC), the child qdisc\u0027s drop-on-dequeue behavior (netem loss/corrupt/nested-child enqueue failure, or aggressive codel parameters), packet injection, and the moment of class deletion; the whole sequence runs serialized under the qdisc/tree lock with no race to win. The absence of a maintainer reproducer reflects effort not spent, not a condition outside attacker control \u2014 the identical primitive in the companion commit 3df275ef0a6a had a reliable reproducer.\nPR:L - The rtnetlink handlers gate on netlink_net_capable(skb, CAP_NET_ADMIN), which is evaluated against the caller\u0027s netns user_ns, so an unprivileged user obtains it simply with `unshare -Urn` and can then create a dummy/veth device plus the full hfsc+netem hierarchy. No real root in the init namespace is needed.\nUI:N - The attacker performs the entire sequence \u2014 qdisc/class setup, packet transmission, and class deletion \u2014 from their own process. No victim action is involved.\nS:U - The corruption stays within the kernel\u0027s own memory and privilege domain, yielding standard local privilege escalation rather than crossing into another security authority such as a hypervisor or IOMMU boundary.\nC:H - The freed struct hfsc_class remains linked in the scheduler\u0027s eligible rbtree and is subsequently dereferenced, so a heap spray of the kmalloc-1k slot lets the attacker read back kernel data through the reclaimed object and its cl-\u003eqdisc pointer chain, giving effectively arbitrary kernel memory disclosure.\nI:H - After the free, hfsc_dequeue() performs an indirect call via qdisc_dequeue_peeked() through sch-\u003edequeue read from the reclaimed object, plus bstats_update() writes and rb_erase()/rb_insert_color() on attacker-controlled node pointers \u2014 a direct control-flow hijack and arbitrary-write primitive leading to full kernel compromise.\nA:H - Even without successful heap grooming, traversing and erasing a freed rbtree node and calling through a stale function pointer reliably produces a kernel oops/panic, and the attacker can trigger it repeatedly for a complete denial of service."
            }
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/2f46d14919c39528c6e540ebc43f90055993eedc"
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          "url": "https://git.kernel.org/stable/c/6ccbda44e2cc3d26fd22af54c650d6d5d801addf"
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      "title": "net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too",
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    "cveId": "CVE-2025-37823",
    "datePublished": "2025-05-08T06:26:16.839Z",
    "dateReserved": "2025-04-16T04:51:23.947Z",
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    "state": "PUBLISHED"
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