CVE-2026-64037

Full vulnerability record from the local CVENow database.

Description

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

CRITICAL

CVSS score

9.8 (v3.1)

Vulnerability status

Modified

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-07-19 16:17:43.947000

Last modified

2026-10-19 21:17:21.430000

View original CVE JSON

{
  "id": "CVE-2026-64037",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-07-19T16:17:43.947",
  "lastModified": "2026-10-19T21:17:21.430",
  "vulnStatus": "Modified",
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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's 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->amsdu_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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      "affectedData": [
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          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
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          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
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