Debian LinuxOperating system · Debian
CVE-2021-20277
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's libldb. Multiple, consecutive leading spaces in an LDAP attribute can lead to an out-of-bounds memory write, leading to a crash of the LDAP server process handling the request. 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 flaw in Samba's libldb allows multiple consecutive leading spaces in an LDAP attribute to trigger an out-of-bounds memory write, causing the LDAP server process to crash. This is a memory safety vulnerability in the LDAP attribute parsing logic.
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 check package manager: 'dpkg -l | grep samba' (Debian) or 'rpm -qa | grep samba' (Fedora)Affected if version is < 4.12.13, OR between 4.13.0-4.13.5 inclusive, OR 4.14.0
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Identify installed libldb versionRun 'ldb-util --version' or check package manager: 'dpkg -l | grep ldb' (Debian) or 'rpm -qa | grep ldb' (Fedora)Affected if libldb version is bundled with Samba and matches vulnerable Samba versions listed above
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Confirm LDAP service is activeCheck if Samba LDAP server (smbd/nmbd with LDAP) or standalone LDAP server (slapd) is running: 'systemctl status slapd' or 'ps aux | grep -E "slapd|smbd" | grep -v grep'Affected if LDAP service is exposed and processing LDAP requests from clients
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Verify LDAP attribute handling is in useCheck LDAP configuration: examine /etc/samba/smb.conf for 'ldap' settings, or check /etc/ldap/slapd.conf (for slapd), looking for 'suffix' or 'base' directives that confirm directory service is configuredAffected if LDAP backend or LDAP authentication is configured and active
System is affected if running a vulnerable Samba/libldb version (less than 4.12.13, between 4.13.0-4.13.5, or exactly 4.14.0) AND the LDAP server component is enabled and processing requests.
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/libldb security update to patch the out-of-bounds write vulnerability. Prioritize patching on systems running LDAP directory services to restore system availability.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,216.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20277 — 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-2021-20277 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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