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CISA KEV · ACTIVELY EXPLOITED
HIGH severity

CVE-2026-7273

HIGH

CVE-2026-7273 is a high-severity (CVSS 8.8) CWE-121 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-09-21) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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…

Published
Updated
Affected
10 products
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-09-21. Federal agencies were required to remediate by 2026-09-24.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-7273.

EPSS Exploitation Probability

via FIRST.org ↗
2.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk
0.00%1.05%2.10%3.16%0.3%0.3%0.3%2.5%2.5%Jul 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-7273 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 384,189 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

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 Products

10 products · 10 configurations
OS
gs1900-8 firmwarezyxel
< 2.90\(aahh.2\)c0
range
OS
gs1900-8hp firmwarezyxel
< 2.90\(aahi.2\)c0
range
OS
gs1900-10hp firmwarezyxel
< 2.90\(aazi.2\)c0
range
OS
gs1900-16 firmwarezyxel
< 2.90\(aahj.2\)c0
range
OS
gs1900-24 firmwarezyxel
< 2.90\(aahl.2\)c0
range
OS
gs1900-24e firmwarezyxel
< 2.90\(aahk.2\)c0
range

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2026-7273 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2026-7273: Memory Corruption (High 8.8, KEV)