How severe is CVE-2020-26574?

CVE-2020-26574 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-26574 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-26574?

CVE-2020-26574 affects Leostream Connection Broker. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-26574?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-26574 published?

CVE-2020-26574 was published on 2020-10-06 and last updated on 2026-06-17.

CVE-2020-26574

CVE-2020-26574 is a critical-severity vulnerability in Leostream Connection Broker with a CVSS 3.x base score of 9.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Critical (CVSS 3.x base score 9.6)
CVSS v2: 9.3
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Leostream Connection Broker
Published: 2020-10-06
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is 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
How severe is CVE-2020-26574?: CVE-2020-26574 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-26574 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-26574?: CVE-2020-26574 affects Leostream Connection Broker. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-26574?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-26574 published?: CVE-2020-26574 was published on 2020-10-06 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:leostream:connection_broker:*:*:*:*:*:*:*:*

More vulnerabilities in Leostream Connection Broker

CVE-2018-18817 — High (CVSS 7.5): The Leostream Agent before Build 7.0.1.0 when used with Leostream Connection Broker 8.2.72 or earlier allows remote…
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CVE-2021-38157 — Medium (CVSS 6.1): LeoStream Connection Broker 9.x before 9.0.34.3 allows Unauthenticated Reflected XSS via the /index.pl user parameter.…
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