CVE-2026-7007

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

publishedCWE-369

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.

Technical severity4.6 mediumCVSS 3.1 · CNA: zephyr

Published2026-07-24Source updated 2026-11-04

Collected2026-11-043 attributed sources

Fixes and workarounds

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: CNA: zephyr

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: [email protected]

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: [email protected]

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
zephyr zephyrproject `zephyr` https://github.com/zephyrproject-rtos/zephyr	≥ 3.5.0; < 4.3.2 (affected, semver) ≥ 4.4.0; < 4.4.2 (affected, semver) Other versions: unaffected	CNA: zephyr

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

NVD applicability configurations (1)

These expressions retain AND/OR operators, negation, and required environmental products. A listed product is not sufficient to establish exposure when additional conditions apply.

[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "4.5.0",
            "versionStartIncluding": "3.5.0",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
3.1 / 4.6 medium	`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	CNA: zephyr
3.1 / 4.6 medium	`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	NVD: [email protected]

Exploit evidence

https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wrf2-79mm-cvw5
exploit · [email protected]

References

https://github.com/zephyrproject-rtos/zephyr/commit/babc0900ed40e6c023ccc26aa1a321f9388b66afCNA: zephyr · patch
https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wrf2-79mm-cvw5CNA: zephyr
https://github.com/zephyrproject-rtos/zephyr/commit/babc0900ed40e6c023ccc26aa1a321f9388b66af[email protected] · Patch
https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wrf2-79mm-cvw5[email protected] · Exploit, Patch, Vendor Advisory

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