CVE-2026-93244 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/sysfb: simpledrm: Improve stride validation
Validate the computed stride against the maximum value INT_MAX.
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Analysis
by VulDB Data Team • 09/25/2026
The recent resolution of a vulnerability within the Linux kernel's Direct Rendering Manager subsystem specifically targets the sysfb and simpledrm components by enhancing stride validation logic. In graphics processing, particularly in framebuffer implementations, the stride represents the number of bytes between the start of one row of pixels and the start of the next row in video memory. This value is critical for correctly rendering images on display devices. The vulnerability arose from insufficient boundary checking when calculating this stride based on screen dimensions and pixel format depth. Without rigorous validation, an attacker or a malformed input source could trigger integer overflow conditions during arithmetic operations that compute the total buffer size required to hold the framebuffer data.
The technical flaw lies in the absence of a check against INT_MAX before allocating memory for the display buffer. When system parameters such as resolution and color depth are processed, the kernel calculates the stride by multiplying width by bytes per pixel. If these values result in an integer overflow, the computed stride wraps around to a small positive number or zero. Subsequently, when the kernel allocates memory based on this flawed calculation using functions like vmalloc or kmalloc with size derived from height multiplied by the wrapped stride, it may allocate significantly less memory than actually required for rendering the full frame buffer. This discrepancy creates a scenario where subsequent write operations to the framebuffer exceed the allocated bounds, leading to heap-based buffer overflows that can corrupt adjacent kernel data structures.
From an operational perspective, this vulnerability poses significant risks including local privilege escalation and system instability. An unprivileged user with access to display devices or virtual console interfaces could potentially exploit this flaw by manipulating input parameters to trigger the integer overflow condition. Successful exploitation allows for arbitrary code execution within the kernel space, granting full control over the operating system. Furthermore, even without malicious intent, certain hardware configurations or unusual resolution settings might inadvertently trigger this bug during normal operation, resulting in kernel panics, display corruption, or system crashes due to memory corruption events affecting critical subsystems.
This issue aligns with CWE-190 Integer Overflow or Wraparound and CWE-787 Out-of-bounds Write, as the root cause is a failure to validate arithmetic results against maximum limits before use in memory allocation functions. In terms of attack vectors, it relates to ATT&CK technique T1203 Exploitation for Client Execution if leveraged through user-facing display interfaces or potentially T1059 Command and Scripting Interpreter if the overflow leads to code execution environments within the kernel context. The mitigation involves enforcing strict upper bounds on computed strides by comparing them against INT_MAX, ensuring that any calculation exceeding this threshold is rejected before memory allocation occurs. This defensive programming practice prevents the allocation of undersized buffers and eliminates the possibility of heap overflows resulting from arithmetic errors in graphics subsystems.