# CVE-2026-7273: Zyxel GS1900 Series stack-based buffer overflow in CGI program

Source: https://junglewise.ai/threats/cve-2026-7273-zyxel-gs1900-series-stack-based-buffer-overflow-in-cgi-program  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-16. Updated: 2026-09-24  
License: CC BY 4.0 with a link back

CVE-2026-7273 · Severity: critical · CVSS 8.8 · Exploited in the wild · Published 2026-06-16

Zyxel GS1900 Series Switches are network switches used in corporate and government environments to manage data traffic. A stack-based buffer overflow flaw in these devices allows attackers to remotely take complete control of the switch without authentication, enabling data interception, network disruption, or lateral movement into protected networks. The vulnerability is actively being exploited by threat actors, making immediate patching critical for organizations using these devices.

Vendors: [Zyxel](https://junglewise.ai/threats/vendors/zyxel).

## Quick answers

**Is CVE-2026-7273 exploited in the wild?** Yes. CVE-2026-7273 is known to be exploited in the wild, first recorded on 21 September 2026. Treat it as urgent.

**How severe is CVE-2026-7273?** Critical severity, with a CVSS score of 8.8, published 16 June 2026.

**Which products and versions are affected?** Zyxel GS1900-10HP Up to 2.90(AAZI.1)C0; Zyxel GS1900-16 Up to 2.90(AAHJ.1)C0; Zyxel GS1900-24 Up to 2.90(AAHL.1)C0; Zyxel GS1900-24E Up to 2.90(AAHK.1)C0; and 6 more.

**Is there a fix for CVE-2026-7273?** 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-2026-7273 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-7273?** Check whether you run Zyxel Gs1900 Series Switches, Zyxel GS1900-10HP, Zyxel GS1900-16 or one of the others listed at an affected version. 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

CVE-2026-7273 is a stack-based buffer overflow vulnerability in the Zyxel GS1900 Series Switches that permits remote code execution. The vulnerability likely results from insufficient input validation in a network-facing service or management interface that accepts untrusted data and writes it to fixed-size stack buffers. Attack is likely network-based and may not require prior authentication. Successful exploitation grants an attacker complete control of the affected switch, allowing arbitrary command execution and system compromise. CISA has confirmed active exploitation in the wild and added the vulnerability to the Known Exploited Vulnerabilities catalog; organizations should check for and apply vendor patches immediately.

## Affected products

- Zyxel GS1900 Series Switches

## Timeline

- 2026-09-21: kev added: Added to CISA KEV Catalog based on evidence of active exploitation

## References

- [https://www.cisa.gov/news-events/alerts/2026/09/21/cisa-adds-one-known-exploited-vulnerability-catalog](https://www.cisa.gov/news-events/alerts/2026/09/21/cisa-adds-one-known-exploited-vulnerability-catalog)

## Related threats

- [Zyxel GS1900 out-of-bounds write in CGI program](https://junglewise.ai/threats/cve-2026-107441-an-out-of-bounds-write-vulnerability-in-the-cgi-program-of-zyxel)