CVE-2021-42076: An issue was discovered in Barrier before 2.3.4

Q: How do I fix CVE-2021-42076?

barrier: upgrade to 2.3.4. Exact commands for each OS are on this page.

Q: Is CVE-2021-42076 being exploited?

CVE-2021-42076 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-42076 affect?

CVE-2021-42076 affects barrier. Severity is high (CVSS 7.5). An issue was discovered in Barrier before 2.3.4. An attacker can cause memory exhaustion in the barriers component (aka the server-side implementation of Barrier) and barrierc by sending long TCP messages.

Q: How urgent is CVE-2021-42076?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2021-42076 is a high-severity flaw (CVSS 7.5) affecting barrier. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in Barrier before 2.3.4. An attacker can cause memory exhaustion in the barriers component (aka the server-side implementation of Barrier) and barrierc by sending long TCP messages.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.6% (top 25%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-11-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: barrier project

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

Am I affected?

Timeline

2021-11-08 04:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

barrier project barrier UPGRADE

Affected: < 2.3.4

Fixed in: 2.3.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy barrier || rpm -q barrier || barrier --version

2. UPGRADE to 2.3.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade barrier

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade barrier

Note

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

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-2021-42076?

barrier: upgrade to 2.3.4. Exact commands for each OS are on this page.

Is CVE-2021-42076 being exploited?

CVE-2021-42076 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-2021-42076 affect?

CVE-2021-42076 affects barrier. Severity is high (CVSS 7.5). An issue was discovered in Barrier before 2.3.4. An attacker can cause memory exhaustion in the barriers component (aka the server-side implementation of Barrier) and barrierc by sending long TCP messages.

How urgent is CVE-2021-42076?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-42075 HIGH 7.5 UPGRADE An issue was discovered in Barrier before 2.3.4
CVE-2021-42074 HIGH 7.5 UPGRADE An issue was discovered in Barrier before 2.3.4
CVE-2021-42073 HIGH 8.2 UPGRADE An issue was discovered in Barrier before 2.4.0
CVE-2021-42072 HIGH 8.8 UPGRADE MITIGATE An issue was discovered in Barrier before 2.4.0

References

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