CVE-2026-45896 Overview
CVE-2026-45896 is a Linux kernel vulnerability in the Intel Discrete Graphics MTD (Memory Technology Device) driver at drivers/mtd/devices/mtd_intel_dg.c. The driver accesses the regions array before the nregions counter that governs its bounds is set. UBSAN flagged the issue as an array-index-out-of-bounds condition at line 750. The defect also causes the initialization loop to silently ignore ENOMEM allocation failures and continue populating subsequent entries. Kernel maintainers resolved the issue by reordering the region count assignment and properly propagating allocation errors. The Linux kernel published the fix on May 27, 2026.
Critical Impact
Local conditions on systems with Intel discrete graphics can trigger out-of-bounds memory access in the kernel MTD driver, leading to undefined behavior and potential denial of service.
Affected Products
- Linux kernel versions containing the mtd_intel_dg driver prior to the fix
- Systems with Intel Discrete Graphics hardware using the MTD subsystem
- Distributions shipping the unpatched drivers/mtd/devices/mtd_intel_dg.c
Discovery Timeline
- 2026-05-27 - CVE-2026-45896 published to NVD
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-45896
Vulnerability Analysis
The vulnerability is an out-of-bounds array access [CWE-129] in the Intel Discrete Graphics MTD driver. The regions array in mtd_intel_dg.c is bounded by the nregions counter. However, the driver code accesses elements of regions before the nregions value is assigned. UBSAN (Undefined Behavior Sanitizer) reports the condition as array-index-out-of-bounds in drivers/mtd/devices/mtd_intel_dg.c:750:15 with index 0 is out of range for type '<unknown> [*]'.
The initialization loop contains a secondary defect: when memory allocation returns ENOMEM, the loop silently swallows the error and continues populating remaining entries. This leaves the driver in a partially initialized state without surfacing the failure to the caller.
Root Cause
The root cause is an ordering bug in the driver initialization sequence. The code dereferences regions[i] before nregions is committed, so any bounds-checking instrumentation sees an array of unknown size. The companion bug is missing error propagation: ENOMEM returns from allocation calls inside the loop are not handled, breaking the contract that downstream code can rely on a fully populated regions array.
Attack Vector
The defect triggers during MTD driver initialization on systems with Intel discrete graphics. An attacker would need local interaction with the affected subsystem to exercise the code path. The primary observable impact is undefined behavior detected by UBSAN, kernel instability, and resource state corruption when allocations fail. No remote attack vector is documented, and no public exploit is available. The EPSS score is 0.017%, reflecting low expected exploitation activity.
No verified exploitation code is available. Refer to the Kernel Commit 721bd22, Kernel Commit 779c592, and Kernel Commit d58fca8 for the upstream fix details.
Detection Methods for CVE-2026-45896
Indicators of Compromise
- Kernel log entries containing UBSAN: array-index-out-of-bounds in drivers/mtd/devices/mtd_intel_dg.c
- Reports of index 0 is out of range for type '<unknown> [*]' referencing the MTD intel-dg driver
- Unexpected MTD device initialization failures on hosts with Intel discrete graphics
Detection Strategies
- Enable CONFIG_UBSAN on test and pre-production kernels to surface the out-of-bounds access during driver load.
- Audit dmesg and persistent kernel logs for UBSAN traces referencing mtd_intel_dg.c line 750.
- Inventory hosts running affected kernel versions with Intel discrete graphics hardware to scope exposure.
Monitoring Recommendations
- Forward kernel ring buffer events to a centralized logging platform and alert on UBSAN signatures.
- Track kernel package versions across the fleet and flag hosts running builds prior to the upstream fix commits.
- Monitor MTD subsystem error counters and allocation failure logs for anomalies during boot.
How to Mitigate CVE-2026-45896
Immediate Actions Required
- Apply the upstream kernel patches referenced in commits 721bd22, 779c592, and d58fca8.
- Update to a distribution kernel release that incorporates the fix for mtd_intel_dg.c.
- Reboot affected systems after kernel package installation to load the patched module.
Patch Information
The fix is committed upstream in the Linux kernel stable tree. Review the Kernel Commit 721bd22, Kernel Commit 779c592, and Kernel Commit d58fca8 for the corrected code that sets nregions before accessing the array and properly returns on ENOMEM.
Workarounds
- Where the patched kernel cannot be deployed immediately, blacklist the mtd_intel_dg module on systems that do not require MTD access to Intel discrete graphics flash.
- Restrict physical and local access to systems running affected kernels until the update is applied.
- Track distribution security advisories for backported fixes corresponding to your kernel branch.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
