CVEs / CVE-2026-7273
CVE-2026-7273: Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
- Known exploited in the CISA KEV catalog since 21 Sep 2026
- high 8.8 CVSS 3.1 (from the CNA)
- EPSS 2.77% chance of exploitation in the next 30 days, higher than 86% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Zyxel GS1900 series switches contain a stack-based buffer overflow vulnerability in the CGI program which could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
Description
A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Zyxel GS1900-48HPv2 firmware | <= 2.90(ABTQ.1)C0 | — |
| Zyxel GS1900-8 firmware | <= 2.90(AAHH.1)C0 | — |
| Zyxel GS1900-8HP firmware | <= 2.90(AAHI.1)C0 | — |
| Zyxel GS1900-10HP firmware | <= 2.90(AAZI.1)C0 | — |
| Zyxel GS1900-16 firmware | <= 2.90(AAHJ.1)C0 | — |
| Zyxel GS1900-24 firmware | <= 2.90(AAHL.1)C0 | — |
| Zyxel GS1900-24E firmware | <= 2.90(AAHK.1)C0 | — |
| Zyxel GS1900-24EP firmware | <= 2.90(ABTO.1)C0 | — |
| Zyxel GS1900-24HPv2 firmware | <= 2.90(ABTP.1)C0 | — |
| Zyxel GS1900-48 firmware | <= 2.90(AAHN.1)C0 | — |
Exploitation
| In CISA KEV since | 21 Sep 2026 |
|---|---|
| Due date for US federal agencies | 24 Sep 2026 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. |
Severity
| CVSS 3.1 | 8.8 highCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-121 |
References
- CVE-2026-7273 on NVD
- CVE-2026-7273 in the CISA KEV catalog
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-stack-based-buffer-overflow-vulnerability-in-gs1900-series-switches-06-16-2026 (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-stack-based-buffer-overflow-vulnerability-in-gs1900-series-switches-06-16-2026 Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-7273 Third Party Advisory, US Government Resource
- https://www.greynoise.io/blog/open-season-on-kapibala-attacker-steals-government-records-wordpress-exploitation Exploit, Third Party Advisory
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
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