CVE-2026-68278

A flaw was found in the Linux kernel's DisplayPort (DP) Multi-Stream Transport (MST) subsystem. This vulnerability involves multiple buffer overflows within the drm_dp_sideband_append_payload() function when handling data from connected devices. A physically connected, malicious DP MST device can exploit this by sending specially crafted messages, leading to memory corruption. This could potentially allow an attacker to cause system instability or execute unauthorized code.

A moderate security impact flaw was found in the Linux kernel's DisplayPort (DP) Multi-Stream Transport (MST) subsystem. The drm_dp_sideband_append_payload() function contains multiple buffer overflow conditions when accumulating sideband reply chunks from a connected device: a zero-length message length field causes an integer underflow that leads to out-of-bounds reads and writes of up to 255 bytes, a chunk length field of up to 63 can write past the end of the 48-byte chunk buffer, and unbounded payload accumulation can overflow the 256-byte message buffer into adjacent memory. A physically connected malicious DP MST device can exploit these flaws by sending forged sideband reply messages, resulting in kernel memory corruption that can crash the system or potentially lead to arbitrary code execution. Red Hat rates this flaw as moderate security impact because exploitation requires physical access to connect a malicious DisplayPort device. The vulnerable code was introduced upstream in the 3.17 kernel, so the kernel and kernel-rt packages in Red Hat Enterprise Linux 6 and 7 are not affected because the vulnerable code is not present. Red Hat Enterprise Linux 8, 9, and 10 (kernel and kernel-rt) and Red Hat In-Vehicle OS 2 (kernel) are affected, and fixes are being pursued through the standard delegated Red Hat kernel maintenance process.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Prevent the 'drm_dp_mst' kernel module from loading to mitigate this vulnerability. This will disable DisplayPort Multi-Stream Transport functionality, which may affect multi-monitor setups using DisplayPort.

To blacklist the module, create a file named /etc/modprobe.d/blacklist-drm_dp_mst.conf with the following content:

blacklist drm_dp_mst

Then, regenerate the initramfs and reboot the system for the changes to take effect:

drancut --force --kver $(uname -r)
reboot

A system reboot is required for the module to be unloaded and the mitigation to be active. This may impact display functionality if DP MST is in use.