CVE-2026-123621: Path Traversal (CVSS 8.8)

Description

Usermin through 2.570 contains a path traversal vulnerability in mailbox/detachall.cgi that allows remote unauthenticated attackers to write files outside the temporary directory via unsanitized attachment filenames. Attackers can email attachments with ../ sequences in filenames, and when the recipient downloads all attachments, files like ~/.forward are overwritten, enabling command execution.

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CVSS v3.1 Score

8.8

HIGH

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

EPSS — Exploit Prediction

0.0098

Probability of exploitation

0.63%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-22 Path Traversal

References

Other References

https://github.com/webmin/usermin https://github.com/webmin/usermin/blob/2.570/mailbox/detachall.cgi#L43-L51 https://github.com/webmin/usermin/commit/cb4614e8319e0932b10533a4d5606debf5f40e14 https://github.com/webmin/usermin/issues/142 https://hackmd.io/@leediay/H144QKY6zl https://www.vulncheck.com/advisories/usermin-through-2.570-path-traversal-file-write-via-detachall-cgi https://hackmd.io/@leediay/H144QKY6zl

Frequently Asked Questions

What is CVE-2026-123621? +

Usermin through 2.570 contains a path traversal vulnerability in mailbox/detachall.cgi that allows remote unauthenticated attackers to write files outside the temporary directory via unsanitized attachment filenames. Attackers can email attachments with ../ sequences in filenames, and when the recipient downloads all attachments, files like ~/.forward are overwritten, enabling command execution. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-123621? +

CVE-2026-123621 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0098, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-123621? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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