CVE-2026-31616

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_phonet: fix skb frags[] overflow in pn_rx_complete() A broken/bored/mean USB host can overflow the skb_shared_info->frags[] array on a Linux gadget exposing a Phonet function by sending an unbounded sequence of full-page OUT transfers. pn_rx_complete() finalizes the skb only when req->actual < req->length, where req->length is set to PAGE_SIZE by the gadget. If the host always sends exactly PAGE_SIZE bytes per transfer, fp->rx.skb will never be reset and each completion will add another fragment via skb_add_rx_frag(). Once nr_frags exceeds MAX_SKB_FRAGS (default 17), subsequent frag stores overwrite memory adjacent to the shinfo on the heap. Drop the skb and account a length error when the frag limit is reached, matching the fix applied in t7xx by commit f0813bcd2d9d ("net: wwan: t7xx: fix potential skb->frags overflow in RX path").

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel (stable branches before commit c088d5dd2fffb4de1fb8e7f57751c8b82942180a)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import usb.core
import usb.util

# Find the USB gadget device
# dev = usb.core.find(idVendor=YOUR_VENDOR_ID, idProduct=YOUR_PRODUCT_ID)
# if dev is None:
#     raise ValueError('Device not found')

PAGE_SIZE = 4096
data = b'A' * PAGE_SIZE
ENDPOINT_OUT = 0x01

try:
    # Send full-page packets continuously to trigger overflow
    for i in range(20): # Sending more than MAX_SKB_FRAGS (17)
        # dev.write(ENDPOINT_OUT, data, timeout=1000)
        print(f"Sending packet {i} of size {PAGE_SIZE}")
except Exception as e:
    print(e)

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31616
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31616
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31616/
[4] VulDB https://vuldb.com/cve/CVE-2026-31616
[5] https://git.kernel.org/stable/c/4e476c25bfcab0535ba7c76a903ae77ca8747711
[6] https://git.kernel.org/stable/c/66f7471c4042e4eb300e30b5b9d87d1406862673
[7] https://git.kernel.org/stable/c/9ceff1251904901b0b4e5fe6350fcaffa368ce83
[8] https://git.kernel.org/stable/c/bd44ce09b9b569f49ed13e2d87d23d853fc7d6a7
[9] https://git.kernel.org/stable/c/c088d5dd2fffb4de1fb8e7f57751c8b82942180a
[10] https://git.kernel.org/stable/c/c9315ce9da3632c591666a29de82d3e92d46bec1

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31616", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:40.870", "lastModified": "2026-04-28T17:21:15.470", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_phonet: fix skb frags[] overflow in pn_rx_complete()\n\nA broken/bored/mean USB host can overflow the skb_shared_info->frags[]\narray on a Linux gadget exposing a Phonet function by sending an\nunbounded sequence of full-page OUT transfers.\n\npn_rx_complete() finalizes the skb only when req->actual < req->length,\nwhere req->length is set to PAGE_SIZE by the gadget. If the host always\nsends exactly PAGE_SIZE bytes per transfer, fp->rx.skb will never be\nreset and each completion will add another fragment via\nskb_add_rx_frag(). Once nr_frags exceeds MAX_SKB_FRAGS (default 17),\nsubsequent frag stores overwrite memory adjacent to the shinfo on the\nheap.\n\nDrop the skb and account a length error when the frag limit is reached,\nmatching the fix applied in t7xx by commit f0813bcd2d9d (\"net: wwan:\nt7xx: fix potential skb->frags overflow in RX path\")."}], "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": "CWE-401"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.32", "versionEndExcluding": "6.6.136", "matchCriteriaId": "B5320F96-8216-44DE-B8AC-7694F1E2D98E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.83", "matchCriteriaId": "7F0AE5B5-23AC-4DCC-B37A-51CA1DAE7BA8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/4e476c25bfcab0535ba7c76a903ae77ca8747711", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/66f7471c4042e4eb300e30b5b9d87d1406862673", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9ceff1251904901b0b4e5fe6350fcaffa368ce83", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/bd44ce09b9b569f49ed13e2d87d23d853fc7d6a7", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c088d5dd2fffb4de1fb8e7f57751c8b82942180a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c9315ce9da3632c591666a29de82d3e92d46bec1", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}