# CVE-2026-31694: fuse: reject oversized dirents in page cache

> A malicious FUSE server can trigger a kernel buffer overflow via oversized directory entries, potentially leading to code execution or privilege escalation.

- **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:** 1 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-85424, BELL-CVE-2026-31694, DEBIAN-CVE-2026-31694, GHSA-8fxx-fj7q-42m6, ROOT-OS-DEBIAN-11-CVE-2026-31694, ROOT-OS-DEBIAN-12-CVE-2026-31694, ROOT-OS-UBUNTU-2204-CVE-2026-31694, ROOT-OS-UBUNTU-2404-CVE-2026-31694, UBUNTU-CVE-2026-31694

## What is CVE-2026-31694?

CVE-2026-31694 is a high-severity memory corruption vulnerability in Linux kernel, published on 1 May 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:

fuse: reject oversized dirents in page cache

fuse_add_dirent_to_cache() computes a serialized dirent size from the
server-controlled namelen field and copies the dirent into a single
page-cache page. The existing logic only checks whether the dirent fits
in the remaining space of the current page and advances to a fresh page
if not. It never checks whether the dirent itself exceeds PAGE_SIZE.

As a result, a malicious FUSE server can return a dirent with
namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB
page systems this causes memcpy() to overflow the cache page by 24 bytes
into the following kernel page.

Reject dirents that cannot fit in a single page before copying them into
the readdir cache.

## Which versions are affected by CVE-2026-31694?

It affects 2 products.


Products: Linux kernel, Siemens Simatic S7-1500 Tm Mfp Firmware.

## How do I fix CVE-2026-31694?

Apply the vendor's patch.

## Is CVE-2026-31694 being exploited?

There is no known exploitation of CVE-2026-31694 in the wild and no public exploit code.

Public exploit code:

- Linux kernel FUSE readdir cache out-of-bounds write (CVE-2026-31694): a malicious FUSE server overflows a page-cache page by 24 bytes. PoC plus an unprivileged local-root exploit via /etc/passwd page-cache corruption. Run only inside a VM. (github_poc): https://github.com/0xCyberstan/CVE-2026-31694-POC

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31694 and fix it if it is affected.

What it is: CVE-2026-31694 is a high-severity memory corruption vulnerability in Linux kernel, published on 1 May 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-2026-31694 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31694/ (Markdown: https://insights.sbomify.com/CVE-2026-31694/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31694
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31694
- OSV: https://osv.dev/vulnerability/CVE-2026-31694

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31694/
Summaries are generated and may contain mistakes; the official description above is the record.