# CVE-2026-7273 — Zyxel GS1900-48HPv2 firmware **CISA KEV** > As of 2026-09-22, CVE-2026-7273 is a HIGH-severity vulnerability in Zyxel GS1900-48HPv2 firmware, CVSS v3.1 8.8, EPSS 0.3% (24.6th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-09-21), with a US federal remediation deadline of 2026-09-24. Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-7273, most recently “Chinese-Speaking 'Kapibala' Actor (Red Heron-Linked) Chains WordPress wp2shell, Zyxel GS1900, and Ubiquiti UniFi OS Flaws to Steal Government Data”. **Last updated:** 2026-09-22 ## What is CVE-2026-7273? 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. The record classifies CVE-2026-7273 under weakness class [CWE-121](https://cwe.mitre.org/data/definitions/121.html). Its CVSS v3 base vector states that the flaw is reachable from an adjacent network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 10 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 104 days ago. ## Severity and exploitation probability - **CVSS v3.1 base score:** 8.8 — HIGH (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 24.6% of all scored CVEs - **CISA KEV:** Listed since 2026-09-21, federal remediation deadline 2026-09-24 - **Threadlinqs priority:** 9/10 — CISA KEV-listed, which Threadlinqs floors at 9 - **Published:** 2026-06-16, last modified 2026-09-22 ## Is CVE-2026-7273 being exploited? CISA added CVE-2026-7273 to the Known Exploited Vulnerabilities catalog on 2026-09-21, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-09-24 under BOD 22-01. It currently carries a trending score of 22 in the Threadlinqs vulnerability feed. ## Affected products and versions - **Zyxel**: GS1900-48HPv2 firmware, GS1900-8 firmware, GS1900-8HP firmware, GS1900-10HP firmware, GS1900-16 firmware, GS1900-24 firmware, GS1900-24E firmware, GS1900-24EP firmware, GS1900-24HPv2 firmware, GS1900-48 firmware ## How to fix CVE-2026-7273 Because CVE-2026-7273 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-09-24. No vendor patch reference has been recorded for CVE-2026-7273 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise. ## Threat activity tracking CVE-2026-7273 2 tracked threats in the Threadlinqs corpus reference CVE-2026-7273, either in the campaign’s CVE list or as an indicator on the campaign record. - [Chinese-Speaking 'Kapibala' Actor (Red Heron-Linked) Chains WordPress wp2shell, Zyxel GS1900, and Ubiquiti UniFi OS Flaws to Steal Government Data](https://intel.threadlinqs.com/threat/TL-2026-2619) — CRITICAL · 2026-09-22 - [Zyxel GS1900 Series Switches Stack-Based Buffer Overflow (CVE-2026-7273) Actively Exploited by Kapibala/Red Heron in Global 996-Device Campaign — Added to CISA KEV](https://intel.threadlinqs.com/threat/TL-2026-2611) — CRITICAL · 2026-09-21 ## Sources Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories. Last verified by Threadlinqs on 2026-09-22. This product uses the NVD API but is not endorsed or certified by the NVD. **Vendor advisory and patch** - [zyxel.com — vendor advisory](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) Canonical: https://intel.threadlinqs.com/cve/CVE-2026-7273 Full detection coverage and IOCs for threats exploiting CVE-2026-7273 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp