CVE-2021-28977

Name: CVE-2021-28977
Creator: NVD / NIST
Published: 2021-06-23T13:15:08.18+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.8/10EPSS 0.51%

Last modified Jun 17, 2026

CVE-2021-28977 is a medium-severity vulnerability rated 4.8/10 on the CVSS scale. Cross Site Scripting vulnerability in GetSimpleCMS 3.3.16 in admin/upload.php by adding comments or jpg and other file header information to the content of xla, pages, and gzip files,. EPSS estimates a 0.51% chance of exploitation in the next 30 days.

Description

Cross Site Scripting vulnerability in GetSimpleCMS 3.3.16 in admin/upload.php by adding comments or jpg and other file header information to the content of xla, pages, and gzip files,

Metrics

CVSS 3.1

4.8/10

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

EPSS Probability

0.51%

39.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Get-Simple	Getsimplecms	<= 3.3.15

References

https://github.com/GetSimpleCMS/GetSimpleCMS/issues/1336Third Party Advisory
https://github.com/GetSimpleCMS/GetSimpleCMS/issues/1336Third Party Advisory

Timeline

Published: Jun 23, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28977?

Cross Site Scripting vulnerability in GetSimpleCMS 3.3.16 in admin/upload.php by adding comments or jpg and other file header information to the content of xla, pages, and gzip files,

How severe is CVE-2021-28977?

CVE-2021-28977 has a CVSS score of 4.8/10 (MEDIUM severity). The EPSS model estimates a 0.51% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28977?

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-2021-28977?

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

Scan your code now

Source: NVD / NIST