CVE-2020-26574: Leostream Connection Broker 8.2.x is affected by stored XSS

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CRITICAL 9.6UPGRADE

CVE-2020-26574 is a critical-severity flaw (CVSS 9.6) affecting connection broker. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	9.6 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	2.1% (top 18%)
CISA exploited list	No
Weakness	CWE-79
Published	2020-10-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: leostream

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-10-06 15:15 UTCPublished CVE record published
2026-06-17 03:08 UTCUpdated Record last modified

leostream connection broker UPGRADE

Affected: >= 8.2.15 and <= 8.2.73

Fixed in: newer than 8.2.73

Safe to downgrade to: a release before 8.2.15

1. Check installed version

apt-cache policy connection-broker || rpm -q connection-broker || connection-broker --version

2. UPGRADE to newer than 8.2.73 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade connection-broker

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade connection-broker

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 8.2.15 (Debian / Ubuntu)

apt-cache madison connection-broker sudo apt install connection-broker=<VERSION_BEFORE_8.2.15> sudo apt-mark hold connection-broker

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list connection-broker sudo dnf downgrade connection-broker-<VERSION_BEFORE_8.2.15> sudo dnf versionlock add connection-broker

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-26574?

connection broker: upgrade to newer than 8.2.73. Exact commands for each OS are on this page.

Is CVE-2020-26574 being exploited?

CVE-2020-26574 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-26574 affect?

CVE-2020-26574 affects connection broker. Severity is critical (CVSS 9.6). 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

How urgent is CVE-2020-26574?

Priority 59/100. Critical severity; Public exploit reference

Software pages

Perl vulnerabilities

Related CVEs

CVE-2021-41551 MEDIUM 4.9 DOWNGRADE Leostream Connection Broker 9.0.40.17 allows administrators to conduct directory traversal attacks by uploadin
CVE-2021-41550 HIGH 7.2 DOWNGRADE Leostream Connection Broker 9.0.40.17 allows administrator to upload and execute Perl code.
CVE-2021-38157 MEDIUM 6.1 UPGRADE LeoStream Connection Broker 9.x before 9.0.34.3 allows Unauthenticated Reflected XSS via the /index.pl user pa

References

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