CVE-2026-63962

Received Received - Intake

USB Type-C Connector Manager Buffer Overflow in Linux Kernel

Publication date: 2026-07-19

Last updated on: 2026-07-20

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes() svdm_consume_modes() checks pmdata->altmodes against the array size once before the loop over the count, but forgot to check the bound at every point in the loop. In the well-behaved SVDM discovery flow this is harmless because each of at most SVID_DISCOVERY_MAX SVIDs contributes at most MODE_DISCOVERY_MAX modes, exactly filling altmode_desc[ALTMODE_DISCOVERY_MAX]. But the CMDT_RSP_ACK handler in tcpm_pd_svdm() does not correlate an incoming ACK with any request the port actually sent. Once port->partner is set, an unsolicited Discover Modes ACK is consumed unconditionally. A broken or malicious port partner can therefore drive altmodes to ALTMODE_DISCOVERY_MAX - 1 via the normal flow, and then send one extra Discover Modes ACK with seven VDOs. Because the pre-loop check passes, the loop could then writes up to five entries past altmode_desc[]. For mode_data_prime the next field in struct tcpm_port is the partner_altmode[] pointer array, which then receives partner-chosen SVID/VDO bytes. Move the bound check inside the loop so the array can never be indexed past ALTMODE_DISCOVERY_MAX regardless of how many VDOs the partner supplies or how the function was reached.

CVSS Scores

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Meta Information

Published

2026-07-19

Last Modified

2026-07-20

Generated

2026-07-20

AI Q&A

2026-07-19

EPSS Evaluated

N/A

NVD

CVE-2026-63962

EUVD

EUVD-2026-45735

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a vulnerability in the Linux kernel's USB Type-C port manager (tcpm). The issue involves a missing bounds check in the svdm_consume_modes() function, which processes USB Type-C alternate mode data. An attacker could exploit this by sending maliciously crafted responses during USB Type-C discovery, potentially writing data beyond allocated memory and manipulating port partner settings.

Detection Guidance

This vulnerability is specific to the Linux kernel's USB Type-C port manager (tcpm) and requires kernel-level detection. Check if your system runs a vulnerable kernel version by running uname -a. Monitor kernel logs for Type-C or USB-related errors using dmesg | grep -i typec or dmesg | grep -i usb.

Impact Analysis

If exploited, this vulnerability could allow an attacker connected via USB Type-C to cause memory corruption, leading to system crashes or arbitrary code execution. It may also enable unauthorized access to sensitive data by manipulating USB device interactions.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a low-level kernel memory safety issue in USB Type-C protocol handling that could allow buffer overflow in the Linux kernel. Compliance impacts would only occur if exploitation led to system instability or unauthorized access, which is not specified in the provided context.

Mitigation Strategies

Update your Linux kernel to the latest stable version provided by your distribution. If an update is not immediately available, disable USB Type-C functionality if not required by blacklisting the tcpm module using echo blacklist tcpm | sudo tee -a /etc/modprobe.d/disable-tcpm.conf && sudo update-initramfs -u.

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