CVE-2021-43099

Name: CVE-2021-43099
Creator: NVD / NIST
Published: 2022-03-28T22:15:09.35+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.9/10EPSS 1.09%

Last modified Jun 17, 2026

CVE-2021-43099 is a medium-severity vulnerability rated 4.9/10 on the CVSS scale. An Archive Extraction (AKA "Zip Slip) vulnerability exists in bbs 5.3 in the UpgradeNow function in UpgradeManageAction.java, which unzips the arbitrary upladed zip file without checking filenames. The vulnerability is exploited using a specially crafted archive that holds directory traversal filenames (e.g. EPSS estimates a 1.09% chance of exploitation in the next 30 days.

Description

An Archive Extraction (AKA "Zip Slip) vulnerability exists in bbs 5.3 in the UpgradeNow function in UpgradeManageAction.java, which unzips the arbitrary upladed zip file without checking filenames. The vulnerability is exploited using a specially crafted archive that holds directory traversal filenames (e.g. ../../evil.exe).

Metrics

CVSS 3.1

4.9/10

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

EPSS Probability

1.09%

61.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-22

Affected Software

Vendor	Product	Versions
Diyhi	Bbs	5.3

References

https://github.com/diyhi/bbs/issues/51Exploit, Third Party Advisory
https://github.com/diyhi/bbs/issues/51Exploit, Third Party Advisory

Timeline

Published: Mar 28, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43099?

How severe is CVE-2021-43099?

CVE-2021-43099 has a CVSS score of 4.9/10 (MEDIUM severity). The EPSS model estimates a 1.09% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43099?

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-2021-43099?

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

Scan your code now

Source: NVD / NIST