CVE-2023-27989 — A buffer overflow vulnerability in the CGI program of the Zyxel NR7101 firmware

A buffer overflow vulnerability in the CGI program of the Zyxel NR7101 firmware versions prior to V1.00(ABUV.8)C0 could allow a remote authenticated attacker to cause denial of service (DoS) conditions by sending a crafted HTTP request to a vulnerable device.

01What is this vulnerability?

A buffer overflow vulnerability in the CGI program of the Zyxel NR7101 firmware versions prior to V1.00(ABUV.8)C0 could allow a remote authenticated attacker to cause denial of service (DoS) conditions by sending a crafted HTTP request to a vulnerable device.

02Affected products

Vendor	Product	Versions
Zyxel	NR7101 firmware	< V1.00(ABUV.8)C0

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-06-05T11:02:54.929Z
• Last modified: 2025-01-08T17:19:22.830Z

09References

• www.zyxel.com — https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advis…