{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-90372",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-90372"
  ],
  "published": "2026-09-17T16:10:40Z",
  "summary": "wifi: mt76: mt7915: avoid nss underflow in mt7915_mcu_get_sta_nss",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: mt76: mt7915: avoid nss underflow in mt7915_mcu_get_sta_nss\n\nIf a peer's VHT/HE MCS map has no supported spatial stream (all fields\n0x3), the loop exits with nss == 0 and the function returned (u8)-1 (255),\nwhich was then written into the firmware sta_rec_bf beamforming fields.\nClamp the result to 0.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.188",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-90372"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2801477c36a19be4f549fe60e54995f03b0ea7b9"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/38f4d6323bcd65e41a691432eddabd2b03acdeee"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/25f753f7f620955a8a51e63e445d8b9076c51396"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e63c6291ecddf94769ab91f9d8cdb6ca939f7fc6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/85bd46ab7674b6d357f9a14791352c65fb09eee9"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6ce78d04c7ea4b66838941b5a4232dd1ee0e2cc7"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ecfd1a07e78c31d81322fb2d81dc468081cc3004"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/4a2f4be532e3ea4e2b536e411793a05aaa51af25"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-09-18T17:55:42Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.1,
      "cvss_v3_severity": "High",
      "scenario": "AV:A - A nearby 802.11 peer supplies the malformed MCS map in the HE Capabilities MCS NSS field of an Association Request. hostapd's NL80211_CMD_NEW_STATION reaches ieee80211_add_station()\u2192sta_link_apply_parameters(), which copies he_mcs_nss_supp; mt76_sta_state(AUTH\u2192ASSOC) then calls mt7915_mcu_get_sta_nss() on that map. WiFi radio range is Adjacent.\nAC:L - The attacker sets every 2-bit NSS field in HE rx_mcs_80 or rx_mcs_160 to 0x3. mt7915_mcu_get_sta_nss() then leaves its nss=8..1 loop with nss==0 and returns (u8)-1 (255) on every association. mac80211 does not reject an all-0x3 HE MCS map (unlike the 0xFFFF VHT check in ieee80211_vht_cap_ie_to_sta_vht_cap()). No race is involved.\nPR:N - mt7915_mac_sta_event(MT76_STA_EVENT_ASSOC) runs from sta_info_move_state(IEEE80211_STA_ASSOC) when hostapd's NL80211_CMD_NEW_STATION sets ASSOCIATED, before AUTHORIZED (the WPA 4-way handshake). 802.11 Open System authentication does not require a PSK or SAE credential on this path.\nUI:N - The attacker transmits the Association Request. ieee80211_add_station() and mt7915_mcu_add_sta() run in the AP kernel with no operator action on the victim device.\nS:U - The underflowed NSS is stored in the kernel sta_rec_bf TLV and sent to the on-device mt7915 MCU via MCU_EXT_CMD(STA_REC_UPDATE). Impact stays in the same kernel/device authority; this is not a VM, IOMMU, or sandbox escape.\nC:N - mt7915_mcu_get_sta_nss() only derives a u8 from the peer MCS map. That 255 is stored in sta_rec_bf.ncol_gt_bw80 or ibf_ncol; ncol used to index matrix[4][4] is min()'d with nrow, so there is no kernel OOB read and nothing is returned over the air.\nI:L - mt7915_mcu_sta_bfer_he() writes the underflowed nss_mcs (255) directly to sta_rec_bf.ncol_gt_bw80 on 160 MHz, and the implicit-VHT path writes it to ibf_ncol, then mt7915_mcu_add_sta() sends that TLV to firmware. That is a limited corruption of the chip beamforming profile, not an arbitrary kernel write.\nA:H - ncol_gt_bw80 and ibf_ncol are NSS counts the mt7915 MCU uses as beamforming dimensions. 255 is far outside the 0\u20133 range implied by the driver's matrix[4][4], so the firmware can hang or crash and take the radio down, and the peer can retrigger it on every association."
    }
  }
}