CVE-2025-38115 (GCVE-0-2025-38115)
Vulnerability from cvelistv5
Published
2025-07-03 08:35
Modified
2026-08-05 11:59
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: sch_sfq: fix a potential crash on gso_skb handling SFQ has an assumption of always being able to queue at least one packet. However, after the blamed commit, sch->q.len can be inflated by packets in sch->gso_skb, and an enqueue() on an empty SFQ qdisc can be followed by an immediate drop. Fix sfq_drop() to properly clear q->tail in this situation. ip netns add lb ip link add dev to-lb type veth peer name in-lb netns lb ethtool -K to-lb tso off # force qdisc to requeue gso_skb ip netns exec lb ethtool -K in-lb gro on # enable NAPI ip link set dev to-lb up ip -netns lb link set dev in-lb up ip addr add dev to-lb 192.168.20.1/24 ip -netns lb addr add dev in-lb 192.168.20.2/24 tc qdisc replace dev to-lb root sfq limit 100 ip netns exec lb netserver netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 &
References
Impacted products
Vendor Product Version
Linux Linux Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
Version: a53851e2c3218aa30b77abd6e68cf1c371f15afe
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            "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
          },
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            "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: sch_sfq: fix a potential crash on gso_skb handling\n\nSFQ has an assumption of always being able to queue at least one packet.\n\nHowever, after the blamed commit, sch-\u003eq.len can be inflated by packets\nin sch-\u003egso_skb, and an enqueue() on an empty SFQ qdisc can be followed\nby an immediate drop.\n\nFix sfq_drop() to properly clear q-\u003etail in this situation.\n\n\nip netns add lb\nip link add dev to-lb type veth peer name in-lb netns lb\nethtool -K to-lb tso off                 # force qdisc to requeue gso_skb\nip netns exec lb ethtool -K in-lb gro on # enable NAPI\nip link set dev to-lb up\nip -netns lb link set dev in-lb up\nip addr add dev to-lb 192.168.20.1/24\nip -netns lb addr add dev in-lb 192.168.20.2/24\ntc qdisc replace dev to-lb root sfq limit 100\n\nip netns exec lb netserver\n\nnetperf -H 192.168.20.2 -l 100 \u0026\nnetperf -H 192.168.20.2 -l 100 \u0026\nnetperf -H 192.168.20.2 -l 100 \u0026\nnetperf -H 192.168.20.2 -l 100 \u0026"
        }
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      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable code is the SFQ qdisc, reached by configuring a qdisc via tc/netlink on a local netdevice and then driving local transmit traffic through it; there is no path for an unauthenticated remote peer to install the qdisc or control the requeue/limit conditions. Per kernel scoring convention, tc/qdisc netlink-configured subsystems are Local.\nAC:L - The attacker controls every precondition \u2014 SFQ limit, the veth/NAPI setup that forces NETDEV_TX_BUSY requeues into gso_skb, the number of flows, and the traffic rate \u2014 so the \"empty SFQ + inflated q.qlen + single-slot drop\" state is reached deterministically, as demonstrated by the upstream reproducer. No race window or uncontrollable memory layout is required.\nPR:L - Creating the veth pair and installing the SFQ qdisc requires only CAP_NET_ADMIN within a network namespace, which any unprivileged local user obtains via `unshare -Urn`; no real root in the init namespace is needed. Basic local user access is therefore sufficient.\nUI:N - The attacker sets up the qdisc and generates the traffic entirely on their own; no victim action, mount, or file open is involved.\nS:U - The corruption occurs in kernel memory and the resulting compromise stays within the same security authority (kernel/host); no VM, IOMMU, or hypervisor boundary is crossed.\nC:H - The stale q-\u003etail leads to slot-\u003eqlen underflowing to 65535, causing sfq_link() to read q-\u003edep[65535] roughly 256 KB out of bounds, and the emptied slot is returned as a fake sk_buff whose contents are read as skb-\u003elen/skb-\u003edata/GSO fields by the transmit path \u2014 both yield disclosure of adjacent kernel memory and, via heap grooming, arbitrary read.\nI:H - sfq_link() performs out-of-bounds writes (`q-\u003edep[65535].next = x` and `sfq_dep_head(q, n)-\u003eprev = x` with n taken from out-of-bounds memory), and the type-confused sfq_slot is ultimately freed into skbuff_head_cache \u2014 an OOB write plus wild free that is leverageable for control-flow hijack and privilege escalation.\nA:H - Dequeuing from the stale empty slot reliably produces a bogus sk_buff handed to the device driver plus out-of-bounds accesses, causing kernel oops/panic (the reported symptom is a crash), and the condition can be re-triggered at will."
            }
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        "dateUpdated": "2026-08-05T11:59:39.505Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c337efb20d6d9f9bbb4746f6b119917af5c886dc"
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        {
          "url": "https://git.kernel.org/stable/c/b44f791f27b14c9eb6b907fbe51f2ba8bec32085"
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        {
          "url": "https://git.kernel.org/stable/c/5814a7fc3abb41f63f2d44c9d3ff9d4e62965b72"
        },
        {
          "url": "https://git.kernel.org/stable/c/9c19498bdd7cb9d854bd3c54260f71cf7408495e"
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        {
          "url": "https://git.kernel.org/stable/c/b4e9bab6011b9559b7c157b16b91ae46d4d8c533"
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          "url": "https://git.kernel.org/stable/c/d1bc80da75c789f2f6830df89d91fb2f7a509943"
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          "url": "https://git.kernel.org/stable/c/82448d4dcd8406dec688632a405fdcf7f170ec69"
        },
        {
          "url": "https://git.kernel.org/stable/c/82ffbe7776d0ac084031f114167712269bf3d832"
        }
      ],
      "title": "net_sched: sch_sfq: fix a potential crash on gso_skb handling",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38115",
    "datePublished": "2025-07-03T08:35:23.750Z",
    "dateReserved": "2025-04-16T04:51:23.986Z",
    "dateUpdated": "2026-08-05T11:59:39.505Z",
    "state": "PUBLISHED"
  },
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}


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