CVE-2021-42073Public exploitNetwork attack vector

Input capture and clipboard overwrite via trusted label

Published Nov 8, 2021 · Updated Aug 4, 2024

Authentication bypass in Barrier before 2.4.0 allows remote attackers to capture server input events and overwrite its clipboard. ClientProxyUnknown::handleData accepts a free-form Hello client name as sufficient identity and starts a full session when it matches a configured label. Network access and knowledge of a valid label are required; the default label is Unnamed, and host-derived labels can be guessed.

CVSS severity8.2
High
EPSS probability1.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Barrier before 2.4.0 allows remote attackers to capture server input events and overwrite its clipboard. ClientProxyUnknown::handleData accepts a free-form Hello client name as sufficient identity and starts a full session when it matches a configured label. Network access and knowledge of a valid label are required; the default label is Unnamed, and host-derived labels can be guessed.

The record

CVE
CVE-2021-42073
Published
Nov 8, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-384, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
8.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-384Session Fixation
T1210Exploitation of Remote Services

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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