EUVD-2026-48588Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Division safety checks
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Alert meAnalysisAIv1 – Jul 26, 2026
Denial of service in Zephyr RTOS versions before 4.5.0 occurs when mounting a crafted ext2 filesystem with zero values in superblock fields s_blocks_per_group or s_inodes_per_group. An attacker with physical access via removable media can trigger a division-by-zero fault on ARM Cortex-M targets, causing a system crash. No other impact beyond availability; no active exploitation or public exploit is known.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Severity by source
AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from Vendor (zephyr) · only source for this CVE.
CVSS VectorVendor: zephyr
DescriptionCVE.org
The Zephyr ext2 file system validates the on-disk superblock in ext2_verify_disk_superblock() (subsys/fs/ext2/ext2_impl.c) before completing a mount. The validator checked the magic number, block size, revision and feature flags, but did not verify that the on-disk fields s_blocks_per_group and s_inodes_per_group are non-zero. Both fields are read directly from the image and are later used as divisors during mount-time initialization.
During mount, get_ngroups() divides and modulos s_blocks_count by s_blocks_per_group (reached via ext2_fetch_block_group() from ext2_init_fs()), and get_itable_entry() divides (ino - 1) by s_inodes_per_group when fetching the root inode (both in subsys/fs/ext2/ext2_diskops.c). A superblock with either field set to zero therefore causes an integer division by zero during the mount sequence.
An attacker who can present a crafted ext2 image to a device that mounts ext2 - removable media such as an SD card or a USB mass-storage device - can trigger this. On ARMv7-M / ARMv8-M-mainline Cortex-M targets, divide-by-zero trapping is enabled (SCB_CCR_DIV_0_TRP), so the division raises a UsageFault that Zephyr treats as a fatal error, producing a denial of service. The impact is limited to availability; the malformed value is consumed only as a divisor.
The fix rejects a zero s_blocks_per_group or s_inodes_per_group in the superblock validator, returning -EINVAL so the mount fails before any block-group or inode I/O occurs.
Threat Intelligence Overview
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SSVC AssessmentENISA
Priority Score
Attack Technique
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