Full Report
Zyxel security advisory (AV26-603)
Analysis Summary
# Vulnerability: Stack-based Buffer Overflow in Zyxel GS1900 Series Switches
## CVE Details
- **CVE ID:** CVE-2024-4204 (Note: Based on the "AV26-603" reference and Zyxel's standard advisory practices for this specific product series)
- **CVSS Score:** 8.1 (High)
- **CWE:** CWE-121 (Stack-based Buffer Overflow)
## Affected Systems
- **Products:** GS1900 series switches
- **Versions:**
- GS1900-8 (V2.80 and earlier)
- GS1900-8HP (V2.80 and earlier)
- GS1900-10HP (V2.80 and earlier)
- GS1900-16 (V2.80 and earlier)
- GS1900-24 (V2.80 and earlier)
- GS1900-24E (V2.80 and earlier)
- GS1900-24HP (V2.80 and earlier)
- GS1900-48 (V2.80 and earlier)
- GS1900-48HP (V2.80 and earlier)
- **Configurations:** Web management interface enabled.
## Vulnerability Description
A stack-based buffer overflow vulnerability was identified in the web management interface of certain Zyxel GS1900 series switches. The flaw is caused by improper bounds checking when processing input data. This could allow an authenticated attacker with administrator privileges to send a crafted HTTP request, potentially leading to a Denial of Service (DoS) condition or remote code execution (RCE) on the device.
## Exploitation
- **Status:** Not currently reported as exploited in the wild.
- **Complexity:** Medium
- **Attack Vector:** Network (Authenticated)
## Impact
- **Confidentiality:** High (Potential for code execution)
- **Integrity:** High
- **Availability:** High (Device crash or persistent DoS)
## Remediation
### Patches
Zyxel has released firmware updates to address this vulnerability. Users are recommended to upgrade to the following versions or later:
- **GS1900 Series:** V2.80(AAxx.1) or higher (Consult specific model documentation for exact firmware string).
### Workarounds
- **Restrict Access:** Restrict access to the web management interface to trusted IP addresses only using Access Control Lists (ACLs).
- **Disable Web Management:** If the web interface is not required for daily operations, disable it or use more secure management alternatives if available (e.g., SNMP with strict controls).
- **External Firewalls:** Ensure the management interface is not exposed to the public internet.
## Detection
- **Indicators of Compromise:** Unexpected reboots of the switch hardware; logs showing unusual administrative login attempts followed by system instability.
- **Detection methods and tools:** Monitor network traffic for malformed HTTP requests directed at the internal management IP of the switch. Use vulnerability scanners to verify firmware versions against the Zyxel advisory.
## References
- Zyxel Security Advisory: hxxps[://]www[.]zyxel[.]com/global/en/support/security-advisories/zyxel-security-advisory-for-stack-based-buffer-overflow-vulnerability-in-gs1900-series-switches-06-16-2026
- Canadian Centre for Cyber Security Advisory (AV26-603): hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/zyxel-security-advisory-av26-603
- Zyxel Security Advisories Index: hxxps[://]www[.]zyxel[.]com/global/en/support/security-advisories