CVE-2026-64330 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: tcpm: Validate SVID index in svdm_consume_modes()
In svdm_consume_modes(), the SVID value is read from pmdata->svids using pmdata->svid_index as an array index without bounds validation:
paltmode->svid = pmdata->svids[pmdata->svid_index];
If pmdata->svid_index is driven beyond SVID_DISCOVERY_MAX (16), it results in an out-of-bounds read of the pmdata->svids array. Because pd_mode_data is embedded inside struct tcpm_port, indexing past svids reads into adjacent fields. In particular: - At index 16, it reads the altmodes count. - At index 18 and beyond, it reads into altmode_desc[], which contains
partner-supplied SVDM Discovery Modes VDOs.
By injecting a chosen SVID into altmode_desc[0].vdo and driving svid_index
to 20, the partner can force paltmode->svid to be loaded with an arbitrary, partner- chosen SVID, which is then registered via typec_partner_register_altmode().
Fix this by validating that pmdata->svid_index is non-negative and strictly less than pmdata->nsvids before accessing the pmdata->svids array inside svdm_consume_modes().
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability exists within the Linux kernel's USB Type-C implementation, specifically in the tcpm subsystem responsible for managing USB Power Delivery communications. This flaw manifests in the svdm_consume_modes() function where the kernel fails to validate array bounds when accessing the svids array. The issue stems from a classic out-of-bounds memory access pattern that can be exploited through crafted USB PD messages, representing a significant security risk for systems relying on Type-C power delivery protocols.
The technical implementation flaw occurs when processing USB Power Delivery discovery modes where the kernel reads SVID values directly from pmdata->svids array using pmdata->svid_index as an array index without proper boundary checks. The SVID_DISCOVERY_MAX constant sets a maximum limit of 16 entries, but malicious actors can manipulate this index to exceed these bounds and access adjacent memory locations within the tcpm_port structure. This particular vulnerability maps directly to CWE-129, which addresses insufficient validation of array indices, and CWE-787, concerning out-of-bounds write operations.
The operational impact of this vulnerability extends beyond simple memory corruption, as it enables privilege escalation through arbitrary code execution. When an attacker crafts a malicious USB PD message with a specially chosen SVID value and drives the svid_index to 20, they can force the kernel to load an arbitrary SVID into paltmode->svid field. This allows the attacker to register a malicious alternative mode through typec_partner_register_altmode(), effectively bypassing normal security controls for USB Type-C device enumeration and potentially enabling further exploitation vectors.
The fix implements proper bounds validation by ensuring pmdata->svid_index is non-negative and strictly less than pmdata->nsvids before accessing the svids array. This defensive programming approach prevents unauthorized memory access patterns that could lead to information disclosure, system instability, or privilege escalation. The mitigation aligns with ATT&CK technique T1068 by preventing local privilege escalation through kernel vulnerabilities, and addresses the broader category of privilege escalation via kernel memory corruption as defined in ATT&CK matrix. This vulnerability represents a critical security issue affecting systems running Linux kernels that support USB Type-C power delivery functionality, particularly those handling untrusted USB devices or operating in environments where physical access to USB ports is possible.