Debian LinuxOperating system · Debian
CVE-2020-27840
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 · uneditedA flaw was found in samba. Spaces used in a string around a domain name (DN), while supposed to be ignored, can cause invalid DN strings with spaces to instead write a zero-byte into out-of-bounds memory, resulting in a crash. The highest threat from this vulnerability is to system availability.
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 memory corruption vulnerability exists in Samba's handling of Distinguished Name (DN) strings. When parsing DN strings containing spaces around the domain name (which should be ignored), the code incorrectly writes a zero-byte to out-of-bounds memory locations, causing a crash and resulting in denial of service.
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
Debian LinuxOperating system
= 9.0= 10.0
FedoraOperating system
= 32= 33= 34>= 4.0.0, < 4.12.13>= 4.13.0, < 4.13.6>= 4.14.0, < 4.14.1CVSS 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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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 installed Samba versionRun 'samba --version' or 'smbstatus --version' or check your package manager (dpkg -l | grep samba or rpm -qa | grep samba)Affected if Version matches the affected ranges: 4.0.0 to <4.12.13, 4.13.0 to <4.13.6, or 4.14.0 to <4.14.1
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Determine if Samba LDAP/AD integration is activeCheck smb.conf for 'ldap' or 'active directory' related settings such as 'security = ads', 'passdb backend = ldap', or 'idmap config * : ldap'Affected if Samba is configured to use LDAP or Active Directory integration, which triggers the DN parsing code path
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Verify Samba process is runningRun 'ps aux | grep smbd' or 'systemctl status smbd' to confirm the Samba daemon is activeAffected if Samba is actively running and serving connections, making the DoS condition reachable
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Check for LDAP client connectionsReview Samba logs or use 'netstat -tlnp | grep smbd' to see if LDAP-based authentication or directory lookups are occurringAffected if Clients are connecting via LDAP/AD authentication, which would exercise the vulnerable DN parsing routine
You are affected if Samba is running a version within the vulnerable ranges AND LDAP/Active Directory integration is enabled, causing the DN string parsing code to execute with the potential for out-of-bounds memory writes.
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 data4.12.134.13.64.14.1
Apply the Samba security patch for CVE-2020-27840 or upgrade to a patched Samba version. This is a code-level fix requiring an update to Samba packages from your distribution vendor.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-27840 — 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-2020-27840 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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