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Chinese Hackers Exploit Zyxel Switch Vulnerability CVE-2026-7273

Chinese Hackers Exploit Zyxel Switch Vulnerability CVE-2026-7273

First seen 22 Sep 2026, 08:53 UTC • •

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ThreatCluster AI
ThreatCluster •September 23, 2026 at 08:26 UTC
  • •CVE-2026-7273 exploited in 996 Zyxel switches across 48 countries.
  • •564 compromised devices used factory default credentials.
  • •CISA mandates federal agencies to patch by September 24, 2026.

A Chinese-speaking threat actor has exploited a stack-based buffer overflow vulnerability (CVE-2026-7273) in Zyxel GS1900 switches, compromising 996 devices across 48 countries since August 17, 2026. The vulnerability allows unauthenticated attackers to execute OS commands via crafted HTTP requests. Zyxel released patches for the affected firmware versions in June 2026, but many devices remained unpatched. GreyNoise reported that 564 of the compromised devices were using factory default credentials, increasing their vulnerability. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-7273 to its Known Exploited Vulnerabilities catalog and mandated federal agencies to patch the flaw by September 24, 2026. The threat actor is believed to be linked to previous attacks on WordPress and Gitea instances. The exploit code was found to be heavily obfuscated, complicating detection efforts.

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Timeline

2026-06-16
Zyxel releases security patches
Patches for CVE-2026-7273 were released to address the stack-based buffer overflow vulnerability.
Zyxel
2026-08-17
Exploitation begins
The threat actor began exploiting CVE-2026-7273, targeting Zyxel GS1900 switches globally.
Helpnetsecurity
2026-09-21
CISA adds CVE-2026-7273 to KEV catalog
CISA added the vulnerability to its Known Exploited Vulnerabilities catalog, urging immediate action.
Securityweek
2026-09-22
CISA mandates patching deadline
Federal agencies are required to patch the vulnerability by September 24, 2026, as per BOD 26-04.
Bleepingcomputer

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