CVE-2026-7007 Division by zero in Zephyr ext2 superblock parsing allows DoS via crafted filesystem image
Attackers can cause denial of service on Zephyr devices by mounting a crafted ext2 filesystem image with zero block or inode group counts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-7007?
CVE-2026-7007 is a medium-severity denial of service vulnerability in Zephyrproject Zephyr, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-369
Which versions are affected by CVE-2026-7007?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-7007?
No fix has been published for CVE-2026-7007 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-7007 being exploited?
There is no known exploitation of CVE-2026-7007 in the wild and no public exploit code.
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Sources
Also known as GHSA-wrf2-79mm-cvw5.