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Zyxel Security Advisory For Stack Based Buffer Overflow Vulnerability In Gs1900 Series Switches 06 16 2026

www.zyxel.com • September 22, 2026

Zyxel has released patches for GS1900 series switches affected by a stack-based buffer overflow vulnerability. Users are advised to install them for optimal protection.

A stack-based buffer overflow vulnerability in the CGI program of the Zyxel GS1900 series switch firmware could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

After a thorough investigation, we identified the vulnerable switch firmware versions and released patches for models still within their vulnerability support period, as shown in the table below. Please note that on-market products not listed in the table remain unaffected.

Please your local service rep or visit Zyxel's Community for further information or assistance.

Thanks to Lei Gu, Jun Cao, Zhiqing Rui, Jingzheng Wu, and Tianyue Luo from ISCAS for reporting the issue to us.

2026-6-16: Initial release

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Zyxel and Veeam Vulnerabilities Under Active Exploitation The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added a critical vulnerability in Zyxel GS1900 series switches (CVE-2026-7273) to its Known Exploited Vulnerabilities catalog due to active exploitation. This stack-based buffer overflow flaw allows unauthenticated attackers to execute OS commands via crafted HTTP requests. Zyxel released patches for affected firmware versions on June 16, 2026, and federal agencies must apply these fixes by September 24, 2026. Concurrently, Arctic Wolf reported active exploitation of a local privilege escalation vulnerability in Veeam Agent for Windows (CVE-2026-32996), enabling attackers with local access to gain SYSTEM-level control. The Veeam vulnerability stems from improper handling of elevated client sessions, and a public proof-of-concept (PoC) was released on September 16, 2026. Both vulnerabilities pose significant risks to organizations using these products. 2 sources 73

Extracted Entities

Zyxel Security Advisory For Stack Based Buffer Overflow Vulnerability In Gs1900 Series Switches 06 16 2026

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Extracted Entities

CWE Weaknesses (1)

MITRE ATT&CK (1)

Platforms (1)