{"id":"CVE-2026-64037","state":"PUBLISHED","title":"wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled","description":"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.","publishedAt":"2026-07-19T15:39:25.435Z","updatedAt":"2026-10-19T20:28:10.404Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"9e360e610a73f62432e986775023d5382773f045","versionType":"git"},{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"cbe1c8245e4469d1aa6e12e5d913611376d23788","versionType":"git"},{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"92cee08dc4f00e77fd1317e4343c5d458b0abab7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/wireless/intel/iwlwifi/mld/tx.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/wireless/intel/iwlwifi/mld/tx.c"]}],"references":["https://git.kernel.org/stable/c/9e360e610a73f62432e986775023d5382773f045","https://git.kernel.org/stable/c/cbe1c8245e4469d1aa6e12e5d913611376d23788","https://git.kernel.org/stable/c/92cee08dc4f00e77fd1317e4343c5d458b0abab7"],"weaknesses":["CWE-20"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64037.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64037","state":"PUBLISHED","datePublished":"2026-07-19T15:39:25.435Z","dateUpdated":"2026-10-19T20:28:10.404Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.028Z"},"containers":{"cna":{"title":"wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled","descriptions":[{"lang":"en","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"9e360e610a73f62432e986775023d5382773f045","versionType":"git"},{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"cbe1c8245e4469d1aa6e12e5d913611376d23788","versionType":"git"},{"version":"d1e879ec600f9b3bdd253167533959facfefb17b","status":"affected","lessThan":"92cee08dc4f00e77fd1317e4343c5d458b0abab7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/wireless/intel/iwlwifi/mld/tx.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/wireless/intel/iwlwifi/mld/tx.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/9e360e610a73f62432e986775023d5382773f045"},{"url":"https://git.kernel.org/stable/c/cbe1c8245e4469d1aa6e12e5d913611376d23788"},{"url":"https://git.kernel.org/stable/c/92cee08dc4f00e77fd1317e4343c5d458b0abab7"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","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's 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's 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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:38:31.759Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64037","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:35:49.759974Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-20","lang":"en","type":"CWE","description":"CWE-20 Improper Input Validation"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:28:10.404Z"}}]}}}