CVE-2026-63963 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: tcpm: validate VDO count in Discover Identity ACK handlers
Properly validate the count passed from a device when calling svdm_consume_identity() or svdm_consume_identity_sop_prime() as the device-controlled value could index off of the static arrays, which could leak data.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides within the Linux kernel's USB type-c subsystem, specifically in the Thunderbolt Control Protocol Manager tcpm implementation where it handles Discover Identity ACK responses from connected devices. The flaw manifests when processing VDO (Vendor Defined Object) counts received from peripheral devices during the identity discovery phase of USB type-c communication protocols. The vulnerability stems from insufficient validation of device-provided count values that determine array indexing operations within kernel memory spaces.
The technical implementation issue occurs when functions svdm_consume_identity() and svdm_consume_identity_sop_prime() process incoming VDO data structures without proper bounds checking on the count parameter. Since these counts are directly derived from device-controlled input rather than being validated against predefined limits, malicious or faulty devices could provide arbitrary values that exceed the static array boundaries allocated for storing identity information. This improper validation creates a classic buffer over-read condition where the kernel attempts to access memory locations beyond the intended array bounds.
The operational impact of this vulnerability extends beyond simple data leakage as it represents a potential pathway for privilege escalation and information disclosure within the kernel space. When a device provides an oversized VDO count, the kernel's memory management routines may inadvertently expose sensitive kernel data structures or memory contents that should remain protected from user-space access. This could potentially allow attackers to extract kernel memory contents including cryptographic keys, credentials, or other confidential system information.
This vulnerability aligns with CWE-129 Input Validation and CWE-787 Out-of-bounds Write categories, representing a failure to properly validate input parameters before using them in memory operations. The flaw also maps to ATT&CK technique T1068, which involves exploiting vulnerabilities in the kernel or operating system to gain elevated privileges, as well as T1547.001 for privilege escalation through kernel exploits. The issue particularly affects systems running Linux kernels with USB type-c support and TCPM implementations that handle device identity discovery protocols.
Mitigation strategies should focus on implementing strict bounds checking for all VDO count parameters before any memory access operations occur. Kernel patches should validate that incoming count values fall within expected ranges before using them to index static arrays, typically by comparing against maximum array dimensions or implementing range checks against predefined limits. Additionally, defensive programming practices such as using safe array access macros and implementing proper input sanitization routines can prevent similar issues in related subsystems. System administrators should ensure timely kernel updates that include the patched tcpm implementation and consider monitoring for anomalous USB device behavior that might indicate exploitation attempts.