# CVE-2026-80656: hfsplus: Add a sanity check for btree node size

> A missing sanity check in the Linux kernel HFS+ driver allows a corrupted image to trigger an uninitialized value bug, causing a system crash.

- **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:** 28 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-80656, GHSA-prqf-3j7q-v843, UBUNTU-CVE-2026-80656

## What is CVE-2026-80656?

CVE-2026-80656 is a high-severity memory corruption vulnerability in Linux, published on 28 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:

hfsplus: Add a sanity check for btree node size

Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
during the file system mounting process, specifically while loading the
catalog, a corrupted node_size value of 1 caused the rec_off argument
passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
large. Consequently, the function failed to return a valid value to
initialize the off variable, triggering the bug [1].

Every node starts from BTree node descriptor: struct hfs_bnode_desc.
So, the size of node cannot be lesser than that. However, technical
specification declares that: "The node size (which is expressed in bytes)
must be power of two, from 512 through 32,768, inclusive." Add a check
for btree node size base on technical specification.

[1]
BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
 hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
 hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
 hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
 get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
 get_tree_bdev+0x38/0x50 fs/super.c:1717
 hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
 vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]

## Which versions are affected by CVE-2026-80656?


## How do I fix CVE-2026-80656?

Apply the vendor's patch.

## Is CVE-2026-80656 being exploited?

There is no known exploitation of CVE-2026-80656 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80656 and fix it if it is affected.

What it is: CVE-2026-80656 is a high-severity memory corruption vulnerability in Linux, published on 28 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-2026-80656 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-2026-80656/ (Markdown: https://insights.sbomify.com/CVE-2026-80656/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80656
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80656
- OSV: https://osv.dev/vulnerability/CVE-2026-80656

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80656/
Summaries are generated and may contain mistakes; the official description above is the record.