# CVE-2026-72369: minix: avoid overflow in bitmap block count calculation

> An integer overflow in the Linux kernel's Minix filesystem allows a local attacker to cause a kernel panic by mounting a crafted image.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72369, DEBIAN-CVE-2026-72369, GHSA-37g9-2p78-fr5w, UBUNTU-CVE-2026-72369

## What is CVE-2026-72369?

CVE-2026-72369 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

minix: avoid overflow in bitmap block count calculation

minix_check_superblock() uses minix_blocks_needed() to verify that the
on-disk imap and zmap block counts are large enough for the advertised
inode and zone counts.

The helper currently performs DIV_ROUND_UP() in unsigned int arithmetic.
A Minix v3 image can set s_ninodes or s_zones near UINT_MAX so the
addition inside DIV_ROUND_UP() wraps to zero. That makes a zero imap/zmap
block count look valid, after which minix_fill_super() can dereference
s_imap[0] or s_zmap[0] even though no bitmap buffers were allocated.

Impact: mounting a crafted Minix v3 image whose s_ninodes or s_zones is
near UINT_MAX makes minix_check_superblock() accept a zero bitmap-block
count and minix_fill_super() dereference s_imap[0]/s_zmap[0], panicking
the kernel.

The divisor is the bitmap capacity in bits, blocksize * 8, which is
always a power of two: minix_fill_super() obtains the block size through
sb_set_blocksize(), and blk_validate_block_size() rejects any size that
is not a power of two. Use DIV_ROUND_UP_POW2(), which divides before
adding the round-up term and so cannot overflow for a power-of-two
divisor.

## Which versions are affected by CVE-2026-72369?


## How do I fix CVE-2026-72369?

Apply the vendor's patch.

## Is CVE-2026-72369 being exploited?

There is no known exploitation of CVE-2026-72369 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72369 and fix it if it is affected.

What it is: CVE-2026-72369 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72369 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72369/ (Markdown: https://insights.sbomify.com/CVE-2026-72369/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72369
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72369
- OSV: https://osv.dev/vulnerability/CVE-2026-72369

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72369/
Summaries are generated and may contain mistakes; the official description above is the record.