CVE-2026-99282 (GCVE-0-2026-99282)

Vulnerability from cvelistv5 – Published: 2026-11-07 14:08 – Updated: 2026-11-07 14:08
VLAI
Title
net/sched: sch_teql: fix use-after-free on lower qdisc drop
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_teql: fix use-after-free on lower qdisc drop The issue: teql_master_xmit() tests the slave's ndo_start_xmit() return value against NETDEV_TX_OK alone. A slave that consumes the skb but returns an error code (rc < NET_XMIT_MASK, e.g. NET_XMIT_DROP) is treated as if the skb were still owned, so the loop restores skb->dev and calls __skb_pull() on it. A VLAN slave returns the result of dev_queue_xmit() from its ndo_start_xmit() (propagated since cbbef5e18307), and when the lower qdisc drops the packet that value is NET_XMIT_DROP after the skb has been freed, giving a use-after-free in teql_master_xmit(). The Fix: test for consumption with dev_xmit_complete(), which accepts NETDEV_TX_OK and every rc < NET_XMIT_MASK, matching other callers that need to distinguish consumed results from busy. Only NETDEV_TX_OK keeps the packet counted in tx_packets/tx_bytes and advances the slave; a consumed result that is neither a success nor NET_XMIT_CN ends the attempt and is charged to tx_dropped, so lower-qdisc drops are no longer reported as good transmits. NET_XMIT_CN is counted like success because it can accompany acceptance of the current packet: pfifo_head_drop drops the old head, enqueues the current skb and returns NET_XMIT_CN. Conditions to recreate the bug: With CONFIG_NET_SCH_TEQL, CONFIG_VLAN_8021Q and CONFIG_DUMMY enabled, add lkrdummy0 (dummy) and lkrvlan0 (VLAN id 37 on lkrdummy0); set a pfifo limit 0 root on lkrdummy0 and a teql0 root on lkrvlan0; bring teql0 up with an address and send one UDP packet to it. The VLAN xmit returns NET_XMIT_DROP from the lower qdisc while holding a freed skb.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6651 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 572a9d7b6fc7f20f573664063324c086be310c42 , < fc55d92ae6a4b2e7d062cad6d4c67f6b061d9cde (git)
Affected: 572a9d7b6fc7f20f573664063324c086be310c42 , < 2702ae318630787c640ec0d0403ffd9d95c43e9e (git)
Affected: 572a9d7b6fc7f20f573664063324c086be310c42 , < 782d6bb8f9b8e9d8591181662222bf74cd3ecf79 (git)
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Linux Linux Affected: 2.6.33
Unaffected: 0 , < 2.6.33 (semver)
Unaffected: 6.18.61 , ≤ 6.18.* (semver)
Unaffected: 7.3.2 , ≤ 7.3.* (semver)
Unaffected: 7.4-rc1 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "net/sched/sch_teql.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_teql: fix use-after-free on lower qdisc drop\n\nThe issue: teql_master_xmit() tests the slave\u0027s ndo_start_xmit() return\nvalue against NETDEV_TX_OK alone. A slave that consumes the skb but\nreturns an error code (rc \u003c NET_XMIT_MASK, e.g. NET_XMIT_DROP) is treated\nas if the skb were still owned, so the loop restores skb-\u003edev and calls\n__skb_pull() on it. A VLAN slave returns the result of dev_queue_xmit()\nfrom its ndo_start_xmit() (propagated since cbbef5e18307), and when the\nlower qdisc drops the packet that value is NET_XMIT_DROP after the skb\nhas been freed, giving a use-after-free in teql_master_xmit().\n\nThe Fix: test for consumption with dev_xmit_complete(), which accepts\nNETDEV_TX_OK and every rc \u003c NET_XMIT_MASK, matching other callers that\nneed to distinguish consumed results from busy. Only NETDEV_TX_OK keeps\nthe packet counted in tx_packets/tx_bytes and advances the slave; a\nconsumed result that is neither a success nor NET_XMIT_CN ends the\nattempt and is charged to tx_dropped, so lower-qdisc drops are no longer\nreported as good transmits. NET_XMIT_CN is counted like success because\nit can accompany acceptance of the current packet: pfifo_head_drop drops\nthe old head, enqueues the current skb and returns NET_XMIT_CN.\n\nConditions to recreate the bug:\nWith CONFIG_NET_SCH_TEQL,\nCONFIG_VLAN_8021Q and CONFIG_DUMMY enabled, add lkrdummy0 (dummy) and\nlkrvlan0 (VLAN id 37 on lkrdummy0); set a pfifo limit 0 root on lkrdummy0\nand a teql0 root on lkrvlan0; bring teql0 up with an address and send one\nUDP packet to it. The VLAN xmit returns NET_XMIT_DROP from the lower\nqdisc while holding a freed skb."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-11-07T14:08:47.978Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/782d6bb8f9b8e9d8591181662222bf74cd3ecf79"
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      "title": "net/sched: sch_teql: fix use-after-free on lower qdisc drop",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99282",
    "datePublished": "2026-11-07T14:08:47.978Z",
    "dateReserved": "2026-09-25T10:25:14.405Z",
    "dateUpdated": "2026-11-07T14:08:47.978Z",
    "state": "PUBLISHED"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_teql: fix use-after-free on lower qdisc drop\n\nThe issue: teql_master_xmit() tests the slave\u0027s ndo_start_xmit() return\nvalue against NETDEV_TX_OK alone. A slave that consumes the skb but\nreturns an error code (rc \u003c NET_XMIT_MASK, e.g. NET_XMIT_DROP) is treated\nas if the skb were still owned, so the loop restores skb-\u003edev and calls\n__skb_pull() on it. A VLAN slave returns the result of dev_queue_xmit()\nfrom its ndo_start_xmit() (propagated since cbbef5e18307), and when the\nlower qdisc drops the packet that value is NET_XMIT_DROP after the skb\nhas been freed, giving a use-after-free in teql_master_xmit().\n\nThe Fix: test for consumption with dev_xmit_complete(), which accepts\nNETDEV_TX_OK and every rc \u003c NET_XMIT_MASK, matching other callers that\nneed to distinguish consumed results from busy. Only NETDEV_TX_OK keeps\nthe packet counted in tx_packets/tx_bytes and advances the slave; a\nconsumed result that is neither a success nor NET_XMIT_CN ends the\nattempt and is charged to tx_dropped, so lower-qdisc drops are no longer\nreported as good transmits. NET_XMIT_CN is counted like success because\nit can accompany acceptance of the current packet: pfifo_head_drop drops\nthe old head, enqueues the current skb and returns NET_XMIT_CN.\n\nConditions to recreate the bug:\nWith CONFIG_NET_SCH_TEQL,\nCONFIG_VLAN_8021Q and CONFIG_DUMMY enabled, add lkrdummy0 (dummy) and\nlkrvlan0 (VLAN id 37 on lkrdummy0); set a pfifo limit 0 root on lkrdummy0\nand a teql0 root on lkrvlan0; bring teql0 up with an address and send one\nUDP packet to it. The VLAN xmit returns NET_XMIT_DROP from the lower\nqdisc while holding a freed skb."
          }
        ],
        "id": "CVE-2026-99282",
        "lastModified": "2026-11-07T14:17:03.940",
        "metrics": {},
        "published": "2026-11-07T14:17:03.940",
        "references": [
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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  }
}



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