Zyxel GS1900 Series Switches Stack-Based Buffer Overflow
Stack-based buffer overflow in Zyxel GS1900 CGI program lets unauthenticated LAN attackers execute OS commands. CVSS 8.8, added to CISA KEV September 21, 2026.
- Vendor
- Zyxel
- Product
- GS1900 Series Switches
- CVSS
- 8.8
- EPSS (exploit probability)
- 2.7%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Published
Is CVE-2026-7273 being exploited?
Yes. CISA added CVE-2026-7273 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 2.7% (scored November 6, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-11-13. Full cross-catalog view: /kev-comparison
CVE-2026-7273 timeline
Every event links to its source. Catalog dates are each catalog's own; day offsets count from NVD publication. Data: JSON
What to do
US federal civilian agencies must remediate by (3 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
CVE-2026-7273 is a stack-based buffer overflow in the CGI program of Zyxel GS1900 series managed switches. A LAN-based, unauthenticated attacker can send a crafted HTTP request to trigger arbitrary OS command execution on the device.
CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on September 21, 2026. Federal Civilian Executive Branch agencies are required to patch by September 24, 2026 under BOD 26-04.
Affected models and patched firmware versions (from Zyxel’s security advisory):
| Model | Fixed version |
|---|---|
| GS1900-8 | 2.90(AAHH.2)C0 |
| GS1900-8HP | 2.90(AAHI.2)C0 |
| GS1900-10HP | 2.90(AAZI.2)C0 |
| GS1900-16 | 2.90(AAHJ.2)C0 |
| GS1900-24 | 2.90(AAHL.2)C0 |
| GS1900-24E | 2.90(AAHK.2)C0 |
| GS1900-24EP | 2.90(ABTO.2)C0 |
| GS1900-24HPv2 | 2.90(ABTP.2)C0 |
| GS1900-48 | 2.90(AAHN.2)C0 |
| GS1900-48HPv2 | 2.90(ABTQ.2)C0 |
Update to the patched firmware version for your model. If you cannot patch immediately, restrict management interface access to trusted hosts and monitor for unusual HTTP requests to the switch CGI. See also NVD record for CVE-2026-7273.
Other Zyxel CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2024-40891 Zyxel DSL CPE OS Command Injection Vulnerability | [ HIGH ] | 8.8 | 22.7% | |
| CVE-2024-40890 Zyxel DSL CPE OS Command Injection Vulnerability | [ HIGH ] | 8.8 | 20.6% | |
| CVE-2024-11667 Zyxel Multiple Firewalls Path Traversal Vulnerabilityransomware use | [ HIGH ] | 7.5 | 3.0% | |
| CVE-2017-6884 Zyxel EMG2926 Routers Command Injection Vulnerabilityransomware use | [ HIGH ] | 8.8 | 33.0% | |
| CVE-2017-18368 Zyxel P660HN-T1A Routers Command Injection Vulnerability | [ CRITICAL ] | 9.8 | 94.5% | |
| CVE-2023-27992 Zyxel Multiple NAS Devices Command Injection Vulnerability | [ CRITICAL ] | 9.8 | 82.3% | |
| CVE-2023-33010 Zyxel Multiple Firewalls Buffer Overflow Vulnerability | [ CRITICAL ] | 9.8 | 29.0% | |
| CVE-2023-33009 Zyxel Multiple Firewalls Buffer Overflow Vulnerability | [ CRITICAL ] | 9.8 | 28.1% |
