What is CVE-2020-26574?

CVE-2020-26574 is a critical-severity vulnerability in Leostream Connection Broker, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2020-10-06.

How severe is CVE-2020-26574?

Critical severity. CVSS v3 base score is 9.6 out of 10.

XSS in Leostream Connection Broker

CVE-2020-26574

Leostream Connection Broker 8.2.x is affected by stored XSS. An unauthenticated attacker can inject arbitrary JavaScript code via the webquery.pl User-Agent HTTP header. It is rendered by the admins the next time they log in. The JavaScript injected can be used to force the admin to upload a malicious Perl script that will be executed as root via libMisc::browser_client. NOTE: This vulnerability only affects products that are no longer supported by the maintainer

Vulnerability class: XSS (Cross-Site Scripting)

Published 2020-10-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.021 (81.2th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 81st percentile — 81.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.021 · newest: 0.021 · change: 0.000

Affected products

Leostream Connection Broker

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

adepts.of0x.cc/leostream-xss-to-rce/ (Exploit, Third Party Advisory)
www.leostream.com/resources/product-lifecycle/ (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2020-26574?: CVE-2020-26574 is a critical-severity vulnerability in Leostream Connection Broker, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2020-10-06.
How severe is CVE-2020-26574?: Critical severity. CVSS v3 base score is 9.6 out of 10.