CVE-2026-64219 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Validate payload length and link_index in dc_process_dmub_aux_transfer_async
[Why&How]
dc_process_dmub_aux_transfer_async() copies payload->length bytes into a 16-byte stack buffer (dpaux.data[16]) guarded only by an ASSERT(), which
is a no-op in release builds. If a caller ever passes length > 16 this results in a stack buffer overflow via memcpy.
Additionally, link_index is used to dereference dc->links[] without
bounds checking against dc->link_count, risking an out-of-bounds access.
Replace the ASSERT with a hard runtime check that returns false when payload->length exceeds the destination buffer size, and add a bounds check for link_index before it is used.
(cherry picked from commit ba4caa9fecdf7a38f98c878ad05a8a64148b6881)
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability in question resides within the AMD display subsystem of the Linux kernel, specifically in the drm/amd/display driver component. This issue affects the dc_process_dmub_aux_transfer_async function which handles asynchronous auxiliary channel transfers for display protocols. The flaw represents a classic buffer overflow vulnerability that could potentially enable arbitrary code execution or system instability when exploited by malicious actors.
The technical implementation of this vulnerability stems from inadequate input validation within the dc_process_dmub_aux_transfer_async function. The function employs a 16-byte stack buffer named dpaux.data[16] to store payload data, yet it only performs an ASSERT() check rather than a robust runtime validation. This assertion mechanism is fundamentally flawed because it becomes inactive in release builds, leaving the system completely unprotected against buffer overflow conditions. When a caller passes a payload length exceeding 16 bytes, the memcpy operation proceeds unchecked, causing direct memory corruption of adjacent stack variables and potentially leading to stack smashing attacks.
The vulnerability extends beyond simple buffer overflows to include additional out-of-bounds memory access through the link_index parameter. This parameter is used as an index to dereference the dc->links[] array without proper bounds checking against dc->link_count, creating another potential vector for memory corruption attacks. The combination of these two flaws creates a particularly dangerous scenario where both stack buffer overflow and out-of-bounds array access can occur simultaneously, amplifying the exploitability of the vulnerability.
From an operational standpoint, this vulnerability represents a significant security risk for systems utilizing AMD graphics hardware through the Linux kernel. Attackers could potentially leverage this flaw to execute arbitrary code with kernel privileges, leading to complete system compromise. The vulnerability affects systems where display protocols are actively used and where the affected driver components are loaded, particularly impacting desktop and server environments with AMD GPU configurations. The exploitability is enhanced by the fact that the ASSERT() check provides no protection in production environments, making this a persistent risk.
The mitigation strategy involves implementing proper runtime checks that replace the ineffective ASSERT() mechanism with robust validation logic. The fix requires adding a hard runtime check to verify that payload->length does not exceed the destination buffer size of 16 bytes, returning false immediately upon detection of oversized payloads rather than allowing the overflow to occur. Additionally, bounds checking must be implemented for link_index before it is used to access the dc->links[] array, ensuring that the index value remains within valid range defined by dc->link_count. This approach aligns with established security practices and follows the principle of defense in depth as outlined in various cybersecurity frameworks.
This vulnerability demonstrates characteristics consistent with CWE-121 Stack-based Buffer Overflow (cwe.mitre.org) and CWE-129 Improper Validation of Array Index (cwe.mitre.org), representing common attack vectors that frequently appear in kernel security assessments. The issue also maps to ATT&CK technique T1068 Exploitation for Privilege Escalation, as successful exploitation would likely result in elevated privileges within the target system. The fix implemented addresses both the immediate buffer overflow condition and the underlying bounds checking deficiency, providing comprehensive protection against potential exploitation while maintaining system functionality and performance characteristics.