CVE-2026-53136 Overview
CVE-2026-53136 is an out-of-bounds heap write vulnerability in the Linux kernel's AMD display driver (drm/amd/display). The flaw resides in the integrated info table parsers get_integrated_info_v11() and get_integrated_info_v2_1(), which read HdmiRegNum and Hdmi6GRegNum fields directly from the Video BIOS (VBIOS). These u8 values drive loop bounds when copying retimer I2C register settings into fixed-size arrays of 9 and 3 entries respectively. A malformed VBIOS supplying values up to 255 triggers a heap buffer overflow during driver probe.
Critical Impact
A crafted or corrupted VBIOS can cause an out-of-bounds heap write during AMD GPU driver initialization, leading to kernel memory corruption and potential denial of service or privilege escalation.
Affected Products
- Linux kernel drm/amd/display subsystem (amdgpu driver)
- Stable branches receiving the backport from upstream commit 5a7f0ef90195
- Systems with AMD GPUs relying on VBIOS integrated info tables v1_11 and v2_1
Discovery Timeline
- 2026-06-25 - CVE-2026-53136 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-53136
Vulnerability Analysis
The AMD display driver parses integrated info tables exposed by the VBIOS to discover platform-specific HDMI retimer configurations. Two parser functions, get_integrated_info_v11() and get_integrated_info_v2_1(), iterate over per-register settings supplied by firmware and copy them into the kernel-resident arrays dp*_ext_hdmi_reg_settings[9] and dp*_ext_hdmi_6g_reg_settings[3].
The loop bounds come from two firmware-controlled u8 fields, HdmiRegNum and Hdmi6GRegNum. The driver did not validate either value before using them as a copy count. Because a u8 can represent values up to 255, a malformed VBIOS produces loop counts far exceeding the destination arrays. The result is a heap out-of-bounds write into adjacent kernel allocations during driver probe.
The upstream fix clamps both counters to the destination array size using min_t() immediately before the copy loops, ensuring the driver writes no more entries than the static arrays hold. The change was backported from commit 5a7f0ef90195940c54b0f5bb85b87da55f038c69 to multiple stable branches.
Root Cause
The root cause is missing input validation on attacker-influenceable firmware data used as a loop bound [CWE-787, CWE-1284]. The driver trusted HdmiRegNum and Hdmi6GRegNum from the VBIOS without bounding them against the fixed-size destination arrays.
Attack Vector
Exploitation requires control over the VBIOS contents read by the AMD GPU at driver load. Realistic attack scenarios include firmware-level tampering by a privileged local actor, supply-chain modification of platform firmware, or physical access to reflash the VBIOS. The vulnerability triggers during driver probe, so corruption manifests at boot or on module load.
No verified public exploit code is available. See the upstream patch commits referenced below for the exact code paths and clamp logic.
Detection Methods for CVE-2026-53136
Indicators of Compromise
- Kernel oops, KASAN reports, or slab corruption messages originating from amdgpu during boot or module load referencing get_integrated_info_v11 or get_integrated_info_v2_1.
- Unexpected GPU driver probe failures or repeated module reload attempts on AMD platforms.
- Anomalous VBIOS dumps showing HdmiRegNum greater than 9 or Hdmi6GRegNum greater than 3.
Detection Strategies
- Enable CONFIG_KASAN on test and pre-production kernels to catch out-of-bounds writes in dp*_ext_hdmi_reg_settings arrays.
- Audit installed kernel versions across the fleet and compare against the stable branches that received the backport commits (029571d, 3f32d52, 4d1c3c2, 5f8b394, 8aaa7e3, d6be8e5, fb0707c).
- Monitor dmesg and persistent kernel logs for amdgpu probe-time faults correlated with firmware updates.
Monitoring Recommendations
- Centralize kernel logs and alert on amdgpu initialization errors, panics, or KASAN reports.
- Track BIOS and VBIOS versions through endpoint inventory tooling and flag unauthorized firmware changes.
- Validate firmware integrity at boot using vendor-signed BIOS update channels and measured boot where available.
How to Mitigate CVE-2026-53136
Immediate Actions Required
- Update to a Linux kernel that includes the upstream fix backported from commit 5a7f0ef90195940c54b0f5bb85b87da55f038c69.
- Apply distribution kernel updates that reference any of the stable commits 029571d, 3f32d52, 4d1c3c2, 5f8b394, 8aaa7e3, d6be8e5, or fb0707c.
- Restrict physical access and privileged local access on systems where firmware tampering is a concern.
Patch Information
The fix clamps HdmiRegNum and Hdmi6GRegNum to the destination array sizes using min_t() in both get_integrated_info_v11() and get_integrated_info_v2_1() before the copy loops execute. Refer to the upstream patch series: Linux Kernel Commit 029571d, Linux Kernel Commit 3f32d52, Linux Kernel Commit 4d1c3c2, Linux Kernel Commit 5f8b394, Linux Kernel Commit 8aaa7e3, Linux Kernel Commit d6be8e5, and Linux Kernel Commit fb0707c.
Workarounds
- Where the AMD display driver is not required, blacklist or unload the amdgpu module until the patched kernel is deployed.
- Enforce signed firmware and disable unauthorized BIOS/VBIOS updates through platform configuration and vendor management tools.
- Apply vendor-supplied BIOS updates that ship validated integrated info tables for affected platforms.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
