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CVE-2026-31623: net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-24 · updated 2026-06-17
• Weakness: CWE-120

Description

In the Linux kernel, the following vulnerability has been resolved: net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete() A malicious USB device claiming to be a CDC Phonet modem can overflow the skb_shared_info->frags[] array by sending an unbounded sequence of full-page bulk transfers. Drop the skb and increment the length error when the frag limit is reached. This matches the same fix that commit f0813bcd2d9d ("net: wwan: t7xx: fix potential skb->frags overflow in RX path") did for the t7xx driver.

Affected products

• Linux kernel: from 2.6.31 before 6.6.136; from 6.7 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; from 7.0 before 7.0.1 — fixed in 6.12.83, 6.18.24, 6.19.14, 6.6.136, 7.0.1

How to fix

Upgrade to a fixed version: Linux kernel 6.12.83, 6.18.24, 6.19.14, 6.6.136. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0c5c65a17db729fc63ab656bdaaf0e675a9dbeac
• https://git.kernel.org/stable/c/600dc40554dc5ad1e6f3af51f700228033f43ea7
• https://git.kernel.org/stable/c/6053620fdbcd89fa7e755644efdaab78e0daaae7
• https://git.kernel.org/stable/c/6807ff49bf796b3823b1e29f97b69316a40a9a94
• https://git.kernel.org/stable/c/9989938d13cc5ba8447eeed5a61acfcf61bc6801
• https://git.kernel.org/stable/c/a23b1b1aaf41e174181d5853a70e65d4d01e648c
• https://git.kernel.org/stable/c/c183d5775129a0a7495bd61a6e57ec230dcf01e5
• https://git.kernel.org/stable/c/d4e1946bea8d6441835eb3fd09b19237ba366a6f
• https://git.kernel.org/stable/c/ebf75c6301c4972a87542ebf2d994c6391eb5d46

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