The Centre for Cybersecurity Belgium warned of a critical OS command injection vulnerability affecting Zyxel EX3510-B0 routers’ UPnP functionality, tracked as CVE-2025-13942 (CVSS 3.1 9.8, CWE-78). Successful exploitation could allow an unauthenticated remote attacker to execute OS commands by sending specially crafted UPnP SOAP requests, potentially leading to full device compromise.
Zyxel published a security advisory covering this issue and recommended customers apply vendor updates; the Belgian advisory similarly urged immediate patching and increased monitoring, noting that updating does not remediate any prior compromise. Separately, Zyxel also disclosed a related but distinct command injection issue in a different model—CVE-2025-13943 in EX3301-T0—which requires authentication and is triggered via the log file download function, and should be tracked and remediated as a separate vulnerability from the EX3510-B0 UPnP flaw.

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4 events from the most recent confirmed update back to the earliest known activity.
Subsequent reporting emphasized that nearly 120,000 Zyxel devices were internet-exposed and that exploitation of CVE-2025-13942 would require both UPnP and WAN access to be enabled. Coverage also noted CISA's tracking of multiple actively exploited Zyxel vulnerabilities and urged prompt patching or replacement of unsupported devices.
Belgium's Centre for Cybersecurity issued a public advisory warning of a critical vulnerability in various Zyxel routers and urged users to patch immediately. The alert amplified official remediation guidance following Zyxel's security release.
Zyxel released security updates for CVE-2025-13942, a critical unauthenticated command-injection vulnerability affecting multiple router, CPE, ONT, and extender models. The company also patched additional command-injection and denial-of-service issues, while noting some CVE-2026-1459 fixes for certain DSL/Ethernet CPE models were planned for March 2026.
Zyxel's security contact received the vulnerability report for CVE-2025-13942, a command injection flaw in the UPnP function of EX3510-B0 firmware. The issue could allow remote OS command execution via crafted UPnP SOAP requests.
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