Division by zero in Zephyr ext2 superblock parsing allows DoS via crafted filesystem image

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-7007
StatePUBLISHED
Assignerzephyr
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-24 15:19:08 UTC
Updated2026-07-27 20:32:27 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 4.6 MEDIUM from [email protected]

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.001550000 probability, percentile 0.051640000 (date 2026-07-29)

Problem Types: CWE-369 | CWE-369 dos | CWE-369 CWE-369 Divide By Zero

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.6MEDIUMCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNACVSS4.6MEDIUMCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Physical
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zephyrproject Zephyr affected 3.5.0 4.5.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/zephyrproject-rtos/zephyr/commit/babc0900ed40e6c023ccc26aa1a3... [email protected] github.com
github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wrf2-79mm-... [email protected] github.com
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