Executive brief
A vulnerability was identified in the Linux kernel's AMD display driver affecting how it handles HDMI connections. When a computer is connected to a malicious or faulty HDMI device (like a repeater), that device could send a specially crafted message that exceeds the computer's memory capacity for that specific task. This could lead to a system crash or potentially allow for unauthorized memory access, impacting the stability and security of the workstation.
Technical details
The vulnerability is an out-of-bounds write located in `mod_hdcp_read_rx_id_list()` within the `drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c` component. During HDCP 2.x repeater authentication over HDMI, the driver reads the sink's RxStatus register and extracts a 10-bit message size field. This value, which can be up to 1023, was used as the read length for the `rx_id_list` without being clamped to the actual destination buffer size of 177 bytes. A malicious HDMI repeater could advertise a message size larger than the buffer, triggering an out-of-bounds write during the I2C read operation. The fix implements a `MIN()` clamp to ensure the read length does not exceed the buffer size.
Affected products
- Linux Linux Kernel 5.6 to 6.13.y
Timeline
- 2026-06-25: disclosed
- 2026-06-25: advisory
References
- https://git.kernel.org/stable/c/1906064d50d194a145486e5caf3db3e708b6f6ef
- https://git.kernel.org/stable/c/3c4444aec06c74fbc05661f370954ac814963c38
- https://git.kernel.org/stable/c/79e0273272a05fb26f9b1e55bf1a52eefc3b7b35
- https://git.kernel.org/stable/c/91fb41218c413989d8b6c837748751454b452d68
- https://git.kernel.org/stable/c/964e50ef7b8f09815a7d05b8326af700f8d5bc96
- https://git.kernel.org/stable/c/98cfb7530ea91d8e5e928285cdce58e1131f6e83
- https://git.kernel.org/stable/c/bfba882cfcd08f6540f72f48e786b6404f5d2c5b