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In the Linux kernel, the following vulnerability has been resolved: usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes()… (CVE-2026-63962)

0
Medium
Published: 07/20/2026 (07/20/2026, 00:00:00 UTC)
Source: GCVE Database
Product: linux

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.

Affected software

Affected versions
<7.0.0-28.28~24.04.1<7.0.0-1016.16~24.04.1<7.0.0-28.28.1~24.04.3<7.0.0-28.28<7.0.0-1009.9

Technical Details

Gcve Source
db.gcve.eu
Osv Id
GHSA-2qj8-cjv3-rxv7
Osv Schema Version
1.4.0
Aliases
["CVE-2026-63962"]
Ecosystems
[]
Database Specific Severity
null
Cvss Version
null

Threat ID: 6a5d27ab2a4a8d598912ef03

Added to database: 07/19/2026, 19:38:19 UTC

Last enriched: 07/19/2026, 20:06:37 UTC

Last updated: 08/26/2026, 23:19:03 UTC

Views: 81

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