CVE-2021-38157: LeoStream Connection Broker 9.x before 9.0.34.3 allows Unauthenticated Reflected XSS via the /index.pl user pa

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MEDIUM 6.1UPGRADE

CVE-2021-38157 is a medium-severity flaw (CVSS 6.1) affecting connection broker. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

LeoStream Connection Broker 9.x before 9.0.34.3 allows Unauthenticated Reflected XSS via the /index.pl user parameter. NOTE: This vulnerability only affects products that are no longer supported by the maintainer

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-06
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

2021-08-06 21:15 UTCPublished CVE record published
2026-06-17 04:01 UTCUpdated Record last modified

leostream connection broker UPGRADE

Affected: >= 9.0.3 and < 9.0.34.3

Fixed in: 9.0.34.3

Safe to downgrade to: a release before 9.0.3

1. Check installed version

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

2. UPGRADE to 9.0.34.3 (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 9.0.3 (Debian / Ubuntu)

apt-cache madison connection-broker sudo apt install connection-broker=<VERSION_BEFORE_9.0.3> 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_9.0.3> 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-2021-38157?

connection broker: upgrade to 9.0.34.3. Exact commands for each OS are on this page.

Is CVE-2021-38157 being exploited?

CVE-2021-38157 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-2021-38157 affect?

CVE-2021-38157 affects connection broker. Severity is medium (CVSS 6.1). LeoStream Connection Broker 9.x before 9.0.34.3 allows Unauthenticated Reflected XSS via the /index.pl user parameter. NOTE: This vulnerability only affects products that are no longer supported by the maintainer

How urgent is CVE-2021-38157?

Priority 43/100. Public exploit reference

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-2020-26574 CRITICAL 9.6 UPGRADE Leostream Connection Broker 8.2.x is affected by stored XSS

References

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