CVE-2021-3906

Name: CVE-2021-3906
Creator: NVD / NIST
Published: 2021-10-27T22:15:07.817+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.65%

Last modified Jun 17, 2026

CVE-2021-3906 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type. EPSS estimates a 0.65% chance of exploitation in the next 30 days.

Description

bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

0.65%

46.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-434

Affected Software

Vendor	Product	Versions
Bookstackapp	Bookstack	< 21.10.1

References

https://github.com/bookstackapp/bookstack/commit/64937ab826b56d086af9ecea532510d37520ebc8Patch, Third Party Advisory
https://huntr.dev/bounties/f115bdf5-c06b-4627-a6fa-ba6904a43ba3Exploit, Issue Tracking, Patch, Third Party Advisory
https://github.com/bookstackapp/bookstack/commit/64937ab826b56d086af9ecea532510d37520ebc8Patch, Third Party Advisory
https://huntr.dev/bounties/f115bdf5-c06b-4627-a6fa-ba6904a43ba3Exploit, Issue Tracking, Patch, Third Party Advisory

Timeline

Published: Oct 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3906?

bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type

How severe is CVE-2021-3906?

CVE-2021-3906 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.65% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3906?

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-2021-3906?

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

Scan your code now

Source: NVD / NIST