CVE-2020-4042
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedBareos before version 19.2.8 and earlier allows a malicious client to communicate with the director without knowledge of the shared secret if the director allows client initiated connection and connects to the client itself. The malicious client can replay the Bareos director's cram-md5 challenge to the director itself leading to the director responding to the replayed challenge. The response obtained is then a valid reply to the directors original challenge. This is fixed in version 19.2.8.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA CRAM-MD5 authentication bypass in Bareos Director where a malicious client can replay the director's own cram-md5 challenge back to it, obtaining a valid authentication response without knowing the shared secret. This works when the director allows client-initiated connections and connects to the client, enabling the replay attack.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 19.2.7= 19.2.8CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Bareos Director versionRun 'bareos-dir --version' or check the installed package version via your system package manager (e.g., dpkg -l bareos-director or rpm -qi bareos-director)Affected if The installed version is 19.2.7 or earlier, or exactly 19.2.8
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Locate the Bareos Director configuration fileThe configuration is typically at /etc/bareos/bareos-dir.conf or /etc/bareos/director.conf. Open the file and search for 'Director' or 'Client' resource definitions.Affected if Configuration file exists and contains director settings
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Verify if client-initiated connections are enabledIn the Director or Client resource configuration, look for directives such as 'Allow Client Connect = yes' or 'Connnect From Client = yes' (the exact directive name varies by Bareos version). This setting permits the director to accept client-initiated connections.Affected if The configuration contains 'Allow Client Connect = yes' or similar setting that allows clients to initiate connections to the director
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Confirm CRAM-MD5 authentication is in useCheck the Director configuration for 'AuthType = CRAM-MD5' or examine the authentication mechanism configured in the Client resource. By default, Bareos uses CRAM-MD5 authentication.Affected if CRAM-MD5 authentication is enabled (this is the default in affected versions)
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Identify which clients are permitted to connectReview all Client resource definitions in the director configuration that have 'Director' or 'Allowed Directory' directives permitting incoming connections. These define which clients could potentially exploit the replay vulnerability.Affected if There are Client resources configured that allow client-initiated connections to the director
You are affected if your Bareos Director version is 19.2.7 or earlier (or exactly 19.2.8) AND client-initiated connections are enabled in the director configuration, allowing CRAM-MD5 authentication replay.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to Bareos version 19.2.8 or later. If immediate upgrading is not feasible, consider disabling client-initiated connections if business requirements allow.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-4042 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-4042 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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