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CVE-2026-64037 (GCVE-0-2026-64037)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-05 12:38
VLAI
Title
wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
Summary
In the Linux kernel, the following vulnerability has been resolved: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled When the TLC notification disables AMSDU for a TID, the MLD driver sets max_tid_amsdu_len to the sentinel value 1. The TSO segmentation path in iwl_mld_tx_tso_segment() checks for zero but not for this sentinel, allowing it to reach the num_subframes calculation: num_subframes = (max_tid_amsdu_len + pad) / (subf_len + pad) = (1 + 2) / (1534 + 2) = 0 This zero propagates to iwl_tx_tso_segment() which sets: gso_size = num_subframes * mss = 0 Calling skb_gso_segment() with gso_size=0 creates over 32000 tiny segments from a single GSO skb. This floods the TX ring with ~1024 micro-frames (the rest are purged), creating a massive burst of TX completion events that can lead to memory corruption and a subsequent use-after-free in TCP's retransmit queue (refcount underflow in tcp_shifted_skb, NULL deref in tcp_rack_detect_loss). The MVM driver is immune because it checks mvmsta->amsdu_enabled before reaching the num_subframes calculation. The MLD driver has no equivalent bitmap check and relies solely on max_tid_amsdu_len, which does not catch the sentinel value. Fix this by detecting the sentinel value (max_tid_amsdu_len == 1) at the existing check and falling back to non-AMSDU TSO segmentation. Also add a WARN_ON_ONCE guard after the num_subframes division as defense-in-depth to catch any future code paths that produce zero through a different mechanism.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d1e879ec600f9b3bdd253167533959facfefb17b , < 9e360e610a73f62432e986775023d5382773f045 (git)
Affected: d1e879ec600f9b3bdd253167533959facfefb17b , < cbe1c8245e4469d1aa6e12e5d913611376d23788 (git)
Affected: d1e879ec600f9b3bdd253167533959facfefb17b , < 92cee08dc4f00e77fd1317e4343c5d458b0abab7 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.34 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/wireless/intel/iwlwifi/mld/tx.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled\n\nWhen the TLC notification disables AMSDU for a TID, the MLD driver sets\nmax_tid_amsdu_len to the sentinel value 1. The TSO segmentation path in\niwl_mld_tx_tso_segment() checks for zero but not for this sentinel,\nallowing it to reach the num_subframes calculation:\n\n  num_subframes = (max_tid_amsdu_len + pad) / (subf_len + pad)\n                = (1 + 2) / (1534 + 2) = 0\n\nThis zero propagates to iwl_tx_tso_segment() which sets:\n\n  gso_size = num_subframes * mss = 0\n\nCalling skb_gso_segment() with gso_size=0 creates over 32000 tiny\nsegments from a single GSO skb. This floods the TX ring with ~1024\nmicro-frames (the rest are purged), creating a massive burst of TX\ncompletion events that can lead to memory corruption and a subsequent\nuse-after-free in TCP\u0027s retransmit queue (refcount underflow in\ntcp_shifted_skb, NULL deref in tcp_rack_detect_loss).\n\nThe MVM driver is immune because it checks mvmsta-\u003eamsdu_enabled before\nreaching the num_subframes calculation. The MLD driver has no equivalent\nbitmap check and relies solely on max_tid_amsdu_len, which does not\ncatch the sentinel value.\n\nFix this by detecting the sentinel value (max_tid_amsdu_len == 1) at the\nexisting check and falling back to non-AMSDU TSO segmentation. Also add\na WARN_ON_ONCE guard after the num_subframes division as defense-in-depth\nto catch any future code paths that produce zero through a different\nmechanism."
        }
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      "metrics": [
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "value": "AV:N - A remote peer can trigger the vulnerable iwlwifi MLD TX/TSO path by inducing large outbound TCP traffic (responses, uploads, or sustained transfers) on a WiFi 7 Intel system; no adjacent WiFi frame injection or local syscall access is required to reach the bug.\nAC:L - An attacker controls the timing and volume of TCP traffic that produces GSO skbs, and TLC AMSDU-disable notifications are normal firmware rate-adaptation behavior that occurs during routine WiFi use; repeated attempts can reliably hit the sentinel state without conditions outside attacker influence.\nPR:N - Exploitation requires only the ability to generate or solicit network traffic on the victim\u0027s WiFi interface; no local account, CAP_NET_ADMIN, or root privileges are needed on the victim host.\nUI:N - No victim user action beyond normal automated network activity is required; a remote attacker can trigger the condition with crafted or high-volume TCP sessions alone.\nS:U - The resulting memory corruption and TCP retransmit-queue UAF occur within kernel/network-driver scope and do not cross a VM, container, or IOMMU security boundary.\nC:H - The fix commit documents memory corruption and a subsequent use-after-free in TCP\u0027s retransmit queue (refcount underflow in tcp_shifted_skb), which per kernel guidance enables arbitrary kernel memory read primitives.\nI:H - The same UAF and refcount corruption in the TCP retransmit path can be leveraged for arbitrary kernel writes and potential control-flow hijacking, not merely a bounded data change.\nA:H - The segmentation explosion floods the TX ring with ~1024 micro-frames and a burst of completion events, causing kernel instability including NULL dereference in tcp_rack_detect_loss and system crash/hang."
            }
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        "dateUpdated": "2026-08-05T12:38:31.759Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/9e360e610a73f62432e986775023d5382773f045"
        },
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          "url": "https://git.kernel.org/stable/c/cbe1c8245e4469d1aa6e12e5d913611376d23788"
        },
        {
          "url": "https://git.kernel.org/stable/c/92cee08dc4f00e77fd1317e4343c5d458b0abab7"
        }
      ],
      "title": "wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64037",
    "datePublished": "2026-07-19T15:39:25.435Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-08-05T12:38:31.759Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-04",
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      "percentile": "0.35984"
    },
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    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-07-20T15:27:33+00:00",
      "cve": "CVE-2026-64037",
      "id": "CVE-2026-64037",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "91",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64037.json",
      "version": "3"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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