CVE-2021-28121

Name: CVE-2021-28121
Creator: NVD / NIST
Published: 2021-08-12T22:15:07.69+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.67%

Last modified Jun 17, 2026

CVE-2021-28121 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Virtual Robots.txt before 1.10 does not block HTML tags in the robots.txt field.. EPSS estimates a 1.67% chance of exploitation in the next 30 days.

Description

Virtual Robots.txt before 1.10 does not block HTML tags in the robots.txt field.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.67%

73.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Virtual Robots.Txt Project	Virtual Robots.Txt	< 1.10

References

https://wordpress.org/plugins/pc-robotstxt/#developersRelease Notes, Vendor Advisory
https://wordpress.org/plugins/pc-robotstxt/#developersRelease Notes, Vendor Advisory

Timeline

Published: Aug 12, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28121?

Virtual Robots.txt before 1.10 does not block HTML tags in the robots.txt field.

How severe is CVE-2021-28121?

CVE-2021-28121 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.67% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28121?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-28121?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST