CVE-2026-98503 (GCVE-0-2026-98503)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:17 – Updated: 2026-10-19 09:20
VLAI
Title
packet: use ubuf_info completion for TX_RING packets
Summary
In the Linux kernel, the following vulnerability has been resolved: packet: use ubuf_info completion for TX_RING packets tpacket_snd sends skbs with frags pointing into its ring slots. Slots are released when skb->destructor is called. A call to skb_orphan calls skb->destructor before the skb is freed. This can cause the slot to be reused while still linked into the skb. Switch to standard zerocopy completion (ubuf_info) so the slot is only released once all references to the payload are freed or copied. Restore skb->destructor to standard sock_wfree. The ubuf_info completion callback can be called with a NULL skb, but only from net_zcopy_put and related API, used by zerocopy implementations that hold their own reference on the uarg, such as MSG_ZEROCOPY. This uarg is only ever completed from skb_zcopy_clear, so skb is always set. To prevent userspace from aliasing in-flight state on shared ring slots, allocate tpacket_uarg per packet, rather than per slot. This adds a small allocation to the transmit path. Use standard kmalloc to allow backporting to stable kernels. The uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt reference. packet_free_tx_ring waits on sk_wmem_alloc before freeing the ring pages. Always allocate vec->deferred for tx_ring so page-backed rings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs before calling tpacket_ubuf_complete. Drop the tx_ring.pg_vec test that tpacket_destruct_skb performed before accessing the slot. The sk_wmem_alloc reference now guarantees that the slot is valid. The test is also not sufficient by itself, as it reads pg_vec without pg_vec_lock, so it can race with packet_set_ring. As a result a slot is released when its payload is copied, which can be before transmission (e.g., in skb_orphan_frags_rx). If copied before skb_tx_timestamp() is called, no slot timestamp is recorded, similar to when skb_orphan() was called early in the datapath before this patch. Revert the now unused previous skb_zcopy_.._nouarg infra. Depends on commit 992cc9f94ca9 ("net/packet: defer vmalloc TX_RING free until skbs finish").
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6971 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5cd8d46ea1562be80063f53c7c6a5f40224de623 , < e67c455d79fbf709a94965f09a2be6bf4f4ba5fd (git)
Affected: 5cd8d46ea1562be80063f53c7c6a5f40224de623 , < eda9bcb721f15a93746a99eabda33d80b86404fd (git)
Affected: 5cd8d46ea1562be80063f53c7c6a5f40224de623 , < 2a0c9afefc0ecea2cc30ccfbbbc98182a0986191 (git)
Affected: 5cd8d46ea1562be80063f53c7c6a5f40224de623 , < 9518405613863d0bf0700927a21367f5942cf058 (git)
Affected: 67f6fba765ef8cb19089d476e3c367212a2fbdfd (git)
Affected: f2a67e68dbaeae7c88e5522873d7b908911f9f77 (git)
Affected: 4.14.86 , < 4.15 (semver)
Affected: 4.19.7 , < 4.20 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 4.20
Unaffected: 0 , < 4.20 (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.55 , ≤ 6.18.* (semver)
Unaffected: 7.2.9 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npacket: use ubuf_info completion for TX_RING packets\n\ntpacket_snd sends skbs with frags pointing into its ring slots. Slots\nare released when skb-\u003edestructor is called.\n\nA call to skb_orphan calls skb-\u003edestructor before the skb is freed.\nThis can cause the slot to be reused while still linked into the skb.\n\nSwitch to standard zerocopy completion (ubuf_info) so the slot is only\nreleased once all references to the payload are freed or copied.\nRestore skb-\u003edestructor to standard sock_wfree.\n\nThe ubuf_info completion callback can be called with a NULL skb, but\nonly from net_zcopy_put and related API, used by zerocopy implementations\nthat hold their own reference on the uarg, such as MSG_ZEROCOPY. This\nuarg is only ever completed from skb_zcopy_clear, so skb is always set.\n\nTo prevent userspace from aliasing in-flight state on shared ring\nslots, allocate tpacket_uarg per packet, rather than per slot. This\nadds a small allocation to the transmit path. Use standard kmalloc to\nallow backporting to stable kernels.\n\nThe uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt\nreference. packet_free_tx_ring waits on sk_wmem_alloc before freeing\nthe ring pages. Always allocate vec-\u003edeferred for tx_ring so page-backed\nrings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs\nbefore calling tpacket_ubuf_complete.\n\nDrop the tx_ring.pg_vec test that tpacket_destruct_skb performed before\naccessing the slot. The sk_wmem_alloc reference now guarantees that the\nslot is valid. The test is also not sufficient by itself, as it reads\npg_vec without pg_vec_lock, so it can race with packet_set_ring.\n\nAs a result a slot is released when its payload is copied, which can\nbe before transmission (e.g., in skb_orphan_frags_rx). If copied\nbefore skb_tx_timestamp() is called, no slot timestamp is recorded,\nsimilar to when skb_orphan() was called early in the datapath before\nthis patch.\n\nRevert the now unused previous skb_zcopy_.._nouarg infra.\n\nDepends on commit 992cc9f94ca9 (\"net/packet: defer vmalloc TX_RING\nfree until skbs finish\")."
        }
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        "shortName": "Linux"
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    "datePublished": "2026-10-18T15:17:03.904Z",
    "dateReserved": "2026-09-25T10:25:14.353Z",
    "dateUpdated": "2026-10-19T09:20:42.115Z",
    "state": "PUBLISHED"
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      "product_status:known_affected": "2",
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      "status": "final",
      "title": "packet: use ubuf_info completion for TX_RING packets",
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      "version": "3"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npacket: use ubuf_info completion for TX_RING packets\n\ntpacket_snd sends skbs with frags pointing into its ring slots. Slots\nare released when skb-\u003edestructor is called.\n\nA call to skb_orphan calls skb-\u003edestructor before the skb is freed.\nThis can cause the slot to be reused while still linked into the skb.\n\nSwitch to standard zerocopy completion (ubuf_info) so the slot is only\nreleased once all references to the payload are freed or copied.\nRestore skb-\u003edestructor to standard sock_wfree.\n\nThe ubuf_info completion callback can be called with a NULL skb, but\nonly from net_zcopy_put and related API, used by zerocopy implementations\nthat hold their own reference on the uarg, such as MSG_ZEROCOPY. This\nuarg is only ever completed from skb_zcopy_clear, so skb is always set.\n\nTo prevent userspace from aliasing in-flight state on shared ring\nslots, allocate tpacket_uarg per packet, rather than per slot. This\nadds a small allocation to the transmit path. Use standard kmalloc to\nallow backporting to stable kernels.\n\nThe uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt\nreference. packet_free_tx_ring waits on sk_wmem_alloc before freeing\nthe ring pages. Always allocate vec-\u003edeferred for tx_ring so page-backed\nrings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs\nbefore calling tpacket_ubuf_complete.\n\nDrop the tx_ring.pg_vec test that tpacket_destruct_skb performed before\naccessing the slot. The sk_wmem_alloc reference now guarantees that the\nslot is valid. The test is also not sufficient by itself, as it reads\npg_vec without pg_vec_lock, so it can race with packet_set_ring.\n\nAs a result a slot is released when its payload is copied, which can\nbe before transmission (e.g., in skb_orphan_frags_rx). If copied\nbefore skb_tx_timestamp() is called, no slot timestamp is recorded,\nsimilar to when skb_orphan() was called early in the datapath before\nthis patch.\n\nRevert the now unused previous skb_zcopy_.._nouarg infra.\n\nDepends on commit 992cc9f94ca9 (\"net/packet: defer vmalloc TX_RING\nfree until skbs finish\")."
          }
        ],
        "id": "CVE-2026-98503",
        "lastModified": "2026-10-19T10:19:03.490",
        "metrics": {},
        "published": "2026-10-18T16:17:01.370",
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        "vulnStatus": "Received"
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      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-30T07:01:38+00:00",
      "cve": "CVE-2026-98503",
      "id": "CVE-2026-98503",
      "initial_release_date": "2026-10-18T00:00:00+00:00",
      "product_status:known_affected": "279",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: packet: use ubuf_info completion for TX_RING packets",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98503.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-10-27T18:02:56Z",
      "cve": "CVE-2026-98503",
      "id": "CVE-2026-98503",
      "initial_release_date": "2026-10-18T23:45:54Z",
      "product_status:known_affected": "255",
      "product_status:known_not_affected": "93",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98503",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98503.json",
      "version": "4"
    }
  }
}



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