CVE-2026-98239 (GCVE-0-2026-98239)

Vulnerability from cvelistv5 – Published: 2026-10-06 08:45 – Updated: 2026-10-07 06:49
VLAI
Title
net: lan743x: fix RX checksum use-after-free
Summary
In the Linux kernel, the following vulnerability has been resolved: net: lan743x: fix RX checksum use-after-free lan743x_rx_process_buffer() adds each non-first receive buffer to the head skb's frag_list. On the last descriptor, lan743x_rx_trim_skb() linearizes the head and frees the fragment skb metadata. The checksum-success path then writes ip_summed through the local skb pointer, which still points to the final fragment. This causes a use-after-free write when a packet spans more than one receive buffer. Set ip_summed on the surviving head skb instead. Multi-buffer receive can occur after a live MTU increase because existing ring entries keep their old buffer size until they are replenished. A KUnit test invoking lan743x_rx_process_buffer() with a two-buffer packet produced a one-byte KASAN use-after-free write before this change. The same test passed after the change. The driver object also builds with W=1. This was not tested on physical LAN743x hardware.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6664 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < 0e52886c4324c9897c2c62f92be3dc8316cee67e (git)
Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < a58024835c704419bb46d2a34e5223f65605f958 (git)
Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < 6fe5c3a2503983abb431d93faeadfc7f5e6a7e33 (git)
Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < 5c216bfa9fb7b36804485e67975e9c98055b31ef (git)
Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < 161a403c8625e152de03d1da22bbf9cda6dc9f9f (git)
Affected: cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a , < a9ce4053dc945c5372dedba5017ee675b30dc0c5 (git)
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Linux Linux Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 6.1.189 , ≤ 6.1.* (semver)
Unaffected: 6.6.158 , ≤ 6.6.* (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.54 , ≤ 6.18.* (semver)
Unaffected: 7.2.8 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix)
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: lan743x: fix RX checksum use-after-free\n\nlan743x_rx_process_buffer() adds each non-first receive buffer to the\nhead skb\u0027s frag_list.  On the last descriptor, lan743x_rx_trim_skb()\nlinearizes the head and frees the fragment skb metadata.\n\nThe checksum-success path then writes ip_summed through the local skb\npointer, which still points to the final fragment.  This causes a\nuse-after-free write when a packet spans more than one receive buffer.\n\nSet ip_summed on the surviving head skb instead.  Multi-buffer receive\ncan occur after a live MTU increase because existing ring entries keep\ntheir old buffer size until they are replenished.\n\nA KUnit test invoking lan743x_rx_process_buffer() with a two-buffer\npacket produced a one-byte KASAN use-after-free write before this change.\nThe same test passed after the change.  The driver object also builds\nwith W=1.  This was not tested on physical LAN743x hardware."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The UAF write runs in lan743x_rx_process_buffer() (NAPI RX) while it handles an ordinary received Ethernet/IP frame from a remote sender. The sender\u0027s frame must be larger than the pre-change buffer size so the chip spreads it across several ring descriptors, which a routed jumbo-MTU path can deliver.\nAC:H - Buffers are sized mtu+ETH_HLEN+FCS+2 and the MAC caps frames at mtu+18 (MAC_RX_FSE_), so multi-buffer frames only occur after an admin raises the MTU on a live interface, while stale ring entries remain, or through the chip\u0027s occasional extra-buffer quirk. The remote attacker cannot produce either condition.\nPR:N - The trigger is a received frame with a valid checksum handled in the NAPI poll path, lan743x_rx_napi_poll -\u003e lan743x_rx_process_buffer. The sender needs no authentication or credentials on the host.\nUI:N - Once the ring holds stale smaller buffers, no user on the victim needs to do anything; sending the oversized frame triggers the stale write. The admin\u0027s MTU change is already counted in AC:H.\nS:U - The freed sk_buff and the corrupted slab memory are inside the kernel itself; no VM, IOMMU or sandbox boundary is crossed.\nC:H - After skb_linearize() in lan743x_rx_trim_skb() frees the frag_list skb, its skbuff_head_cache slot can be reused by another skb. The stale write then hits a live object the attacker can steer with packet timing, which counts as a use-after-free per the scoring guidance.\nI:H - skb-\u003eip_summed = CHECKSUM_UNNECESSARY is written into a freed sk_buff. If the slot has been reallocated, this corrupts another live skb and can make the stack accept forged or corrupted packets without checking their checksums. It is heap memory corruption.\nA:H - Writing into a freed and possibly reused sk_buff from the RX softirq can corrupt slab state and oops or panic the kernel; KASAN flagged the write in the author\u0027s KUnit reproducer."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-07T06:49:35.177Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/0e52886c4324c9897c2c62f92be3dc8316cee67e"
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        {
          "url": "https://git.kernel.org/stable/c/a58024835c704419bb46d2a34e5223f65605f958"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98239",
    "datePublished": "2026-10-06T08:45:10.611Z",
    "dateReserved": "2026-09-25T10:25:14.329Z",
    "dateUpdated": "2026-10-07T06:49:35.177Z",
    "state": "PUBLISHED"
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      "cve": "CVE-2026-98239",
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      "product_status:fixed": "1",
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: lan743x: fix RX checksum use-after-free",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98239.json",
      "version": "3"
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: lan743x: fix RX checksum use-after-free\n\nlan743x_rx_process_buffer() adds each non-first receive buffer to the\nhead skb\u0027s frag_list.  On the last descriptor, lan743x_rx_trim_skb()\nlinearizes the head and frees the fragment skb metadata.\n\nThe checksum-success path then writes ip_summed through the local skb\npointer, which still points to the final fragment.  This causes a\nuse-after-free write when a packet spans more than one receive buffer.\n\nSet ip_summed on the surviving head skb instead.  Multi-buffer receive\ncan occur after a live MTU increase because existing ring entries keep\ntheir old buffer size until they are replenished.\n\nA KUnit test invoking lan743x_rx_process_buffer() with a two-buffer\npacket produced a one-byte KASAN use-after-free write before this change.\nThe same test passed after the change.  The driver object also builds\nwith W=1.  This was not tested on physical LAN743x hardware."
          }
        ],
        "id": "CVE-2026-98239",
        "lastModified": "2026-10-07T07:17:05.810",
        "metrics": {
          "cvssMetricV31": [
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              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
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                "baseScore": 8.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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          }
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        "vulnStatus": "Received"
      }
    },
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      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-09T07:19:15+00:00",
      "cve": "CVE-2026-98239",
      "id": "CVE-2026-98239",
      "initial_release_date": "2026-10-06T00:00:00+00:00",
      "product_status:known_affected": "77",
      "product_status:known_not_affected": "200",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: lan743x: fix RX checksum use-after-free",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98239.json",
      "version": "3"
    }
  }
}



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