CVE-2026-63962

Technical 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

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References