# CVE-2026-77555: Ubiquiti UniFi Gateway out-of-bounds write denial of service

Source: https://junglewise.ai/threats/cve-2026-77555-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-2026-77555 · Severity: high · CVSS 7.5 · Published 2026-09-22

Ubiquiti UniFi gateway devices contain an out-of-bounds memory writing flaw that allows a network-connected attacker to crash the gateway and disrupt network connectivity. An attacker with access to the network can trigger this vulnerability to cause a denial of service, taking the device offline and potentially disrupting business operations that depend on the gateway for internet access or routing.

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

## Quick answers

**Is CVE-2026-77555 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77555 being exploited in the wild.

**How severe is CVE-2026-77555?** 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-2026-77555?** 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-2026-77555 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-77555?** 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 write vulnerability exists in certain UniFi gateway devices that allows an attacker with network access to write data beyond allocated memory boundaries. By exploiting this memory corruption issue, an attacker can crash the gateway process or the device itself, resulting in denial of service. The vulnerability requires network access but no authentication.

## 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)
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- [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)