CVE-2019-12581 — A reflective Cross-site scripting (XSS) vulnerability in the free_time_failed

A reflective Cross-site scripting (XSS) vulnerability in the free_time_failed.cgi CGI program in selected Zyxel ZyWall, USG, and UAG devices allows remote attackers to inject arbitrary web script or HTML via the err_msg parameter.

01What is this vulnerability?

A reflective Cross-site scripting (XSS) vulnerability in the free_time_failed.cgi CGI program in selected Zyxel ZyWall, USG, and UAG devices allows remote attackers to inject arbitrary web script or HTML via the err_msg parameter.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

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: 2019-06-27T14:10:08.000Z
• Last modified: 2024-08-04T23:24:39.189Z

09References

• www.zyxel.com — https://www.zyxel.com/us/en/
• www.zyxel.com — https://www.zyxel.com/support/vulnerabilities-related-to-the-Free-Time-feature.s…
• sec-consult.com — https://sec-consult.com/en/blog/advisories/reflected-cross-site-scripting-in-zxe…
• n-thumann.de — https://n-thumann.de/blog/zyxel-gateways-missing-access-control-in-account-gener…