# CVE-2026-77556: Ubiquiti UniFi gateway out-of-bounds read denial of service

Source: https://junglewise.ai/threats/cve-2026-77556-a-malicious-actor-with-access-to-the-network-could-exploit-an-out  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-77556 · Severity: high · CVSS 7.5 · Published 2026-09-22

UniFi gateway devices, which provide network connectivity and security for organizations, contain an out-of-bounds read flaw that allows a network-adjacent attacker to crash the device and disrupt network operations. A successful exploit results in temporary unavailability of network gateway services, affecting business connectivity and potentially interrupting critical communications.

Technologies: [Ubiquiti UniFi Gateway](https://junglewise.ai/threats/technologies/unifi-gateway). Vendors: [Ubiquiti](https://junglewise.ai/threats/vendors/ubiquiti).

## Quick answers

**Is CVE-2026-77556 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77556 being exploited in the wild.

**How severe is CVE-2026-77556?** High severity, with a CVSS score of 7.5, published 22 September 2026.

**Which products and versions are affected?** Ubiquiti UniFi Gateway.

**Is there a fix for CVE-2026-77556?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-77556 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-77556?** Check whether you run Ubiquiti UniFi Gateway. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read vulnerability in UniFi gateway firmware allows a network-adjacent attacker to read memory beyond intended boundaries, leading to a denial of service condition. The vulnerability requires network access to the affected device and can be exploited without authentication. Exploitation crashes the gateway, disrupting network traffic and services until the device is restarted.

## Affected products

- Ubiquiti UniFi Gateway

## Timeline

- 2026-09-22: disclosed

## References

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

## Related threats

- [Ubiquiti UniFi gateway out-of-bounds write denial of service](https://junglewise.ai/threats/cve-2026-95862-a-malicious-actor-with-access-to-the-network-could-exploit-an-out)
- [Ubiquiti UniFi Gateway uncontrolled recursion denial of service](https://junglewise.ai/threats/cve-2026-95861-a-malicious-actor-with-access-to-the-network-could-exploit-an)
- [Ubiquiti UniFi Gateway out-of-bounds read DoS](https://junglewise.ai/threats/cve-2026-77558-a-malicious-actor-with-access-to-the-network-could-exploit-an-out)
- [Ubiquiti UniFi Gateway out-of-bounds write denial of service](https://junglewise.ai/threats/cve-2026-77555-a-malicious-actor-with-access-to-the-network-could-exploit-an-out)
- [Ubiquiti UniFi Gateway out-of-bounds write denial of service](https://junglewise.ai/threats/cve-2026-77544-a-malicious-actor-with-access-to-the-network-could-exploit-an-out)