# CVE-2026-45699: Netatalk has Integer Underflow → Stack Buffer Overflow in copydir()

> An integer underflow in Netatalk's afpd daemon allows stack buffer overflows, potentially enabling remote code execution when file operations cross device boundaries.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-45699, GHSA-fphv-pf29-p77m, UBUNTU-CVE-2026-45699

## What is CVE-2026-45699?

CVE-2026-45699 is a high-severity vulnerability in netatalk, published on 14 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Netatalk is a Free and Open Source file server suite for Unix-like operating systems. In versions 3.1.19 through 4.4.2, a  stack-based buffer overflow exists in the copydir() function of Netatalk's afpd daemon due to an integer underflow in the calculation of the remaining buffer size used for path construction. copydir() is a utility function called when a file operation crosses a device boundary inside an AFP shared volume, which the standard library's renameat() cannot handle. The function attempts to track available buffer space using srem and drem for source and destination paths. Incorrect arithmetic causes both srem and drem to underflow to SIZE_MAX. Consequently, boundary checks against strlen(de->d_name) always pass, allowing strcpy() to append filenames into nearly full stack buffers. Version 4.4.3 patches the issue. As a workaround, configure each AFP shared volume to be structured as a single file system, in other words no subdirectory of a shared volume should be a mount point for a different file system.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-45699?


## How do I fix CVE-2026-45699?

Apply the vendor's patch.

## Is CVE-2026-45699 being exploited?

There is no known exploitation of CVE-2026-45699 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45699 and fix it if it is affected.

What it is: CVE-2026-45699 is a high-severity vulnerability in netatalk, published on 14 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-45699 in the wild and no public exploit code.

Affected product: netatalk. 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-2026-45699/ (Markdown: https://insights.sbomify.com/CVE-2026-45699/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45699
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45699
- OSV: https://osv.dev/vulnerability/CVE-2026-45699

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45699/
Summaries are generated and may contain mistakes; the official description above is the record.