CVE-2026-98722 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
mtd: block2mtd: Fix divide error when erase_size is zero
The erase size is parsed from the "block2mtd" module parameter and can be set to zero. add_device() then evaluates
if (size % erase_size)
with a zero divisor, which triggers a divide error:
divide error: 0000 [#1] PREEMPT SMP PTI
RIP: 0010:add_device drivers/mtd/devices/block2mtd.c:296 [inline]
RIP: 0010:block2mtd_setup2+0x592/0xda0 drivers/mtd/devices/block2mtd.c:459 Call Trace: block2mtd_setup+0x27/0xe0 drivers/mtd/devices/block2mtd.c:476 param_attr_store+0x214/0x310 kernel/params.c:589 module_attr_store+0x65/0x90 kernel/params.c:904 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345 ...
Reject a zero erase size before performing the modulo operation so the existing "erasesize must be a divisor of device size" error path reports the invalid argument and frees the device.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Memory Technology Device subsystem includes the block2mtd module, which allows users to treat standard block devices as MTD (Memory Technology Device) partitions for flash emulation purposes. This functionality is critical in embedded systems and virtualized environments where physical NAND or NOR flash interfaces are abstracted away in favor of generic storage backends. The configuration of this module relies on kernel parameters passed at runtime, specifically the erase_size parameter which dictates how logical blocks map to underlying hardware erasure units. A recent investigation revealed a critical arithmetic flaw within the add_device function that handles device initialization when an invalid erase size is provided by the user or administrator.
The core technical vulnerability stems from a lack of input validation prior to performing modulo operations on the erase_size variable. When the block2mtd module loads, it parses the erase_size parameter and attempts to verify its compatibility with the target device's total capacity using the expression if (size % erase_size). If an attacker or misconfigured system sets this parameter to zero, the kernel executes a division by zero operation. In Linux kernel space, such arithmetic errors are not handled gracefully but instead trigger a fatal exception known as a divide error. This results in an immediate panic of the current execution context, often leading to a complete system crash if the affected code path is executed during critical boot sequences or hot-plug events. The stack trace confirms that this fault occurs within add_device and propagates through block2mtd_setup2 and param_attr_store, indicating that the vulnerability can be triggered via standard kernel parameter interfaces without requiring elevated privileges beyond those needed to load modules or write to sysfs parameters depending on system configuration.
From a security perspective, this flaw represents a classic Denial of Service vector arising from improper input validation. While it does not directly allow for arbitrary code execution or privilege escalation in its current state, the resulting kernel panic effectively denies service to all processes running on the affected host. In cloud environments or critical infrastructure where system availability is paramount, such instability poses significant operational risks. The vulnerability aligns with CWE-369, which describes divide by zero errors, and falls under MITRE ATT&CK technique T1499, Endpoint Denial of Service, as it disrupts the normal operation of the operating system through resource exhaustion or crash induction via malformed input parameters.
To mitigate this risk, developers have implemented a strict validation check that rejects any erase_size value equal to zero before the modulo arithmetic is attempted. This fix ensures that instead of crashing the kernel, the module correctly identifies the invalid argument and follows the existing error handling path designed for such cases. The system will report an appropriate invalid argument error code and safely free allocated resources associated with the device initialization process. Administrators should ensure their systems are updated to include this patch, particularly in environments where block2mtd is actively used or where kernel parameters can be modified dynamically via sysfs interfaces. Regular auditing of module parameter configurations and enforcing strict input validation policies at the user-space boundary further reduces the attack surface for similar arithmetic vulnerabilities within the Linux kernel subsystems.