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Ubuntu LinuxOperating system · Canonical

CVE-2020-8621

HIGH · 7.5 CVSS v3.1 Published 2020-08-21
Fix available
A fix is available. Upgrade to 2.2.2-5027 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
In BIND 9.14.0 -> 9.16.5, 9.17.0 -> 9.17.3, If a server is configured with both QNAME minimization and 'forward first' then an attacker who can send queries to it may be able to trigger the condition that will cause the server to crash. Servers that 'forward only' are not affected.

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 confidence

In BIND 9 versions 9.14.0->9.16.5 and 9.17.0->9.17.3, a denial-of-service vulnerability exists when a server is configured with both QNAME minimization and 'forward first' options enabled. An attacker who can send DNS queries to the affected server can trigger a crash condition. Servers configured with 'forward only' are not vulnerable.

MitigationDisable QNAME minimization in the server configuration, change 'forward first' to 'forward only', or upgrade to BIND 9.16.6+, 9.17.4+, or a later stable version.

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
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04= 20.04
BindApplication
Affected:>= 9.14.0, <= 9.16.5>= 9.17.0, <= 9.17.3
LeapOperating system
Affected:= 15.1= 15.2
Dns ServerApplication
Affected:< 2.2.2-5027
Steelstore Cloud Integrated StorageApplication
Affected:all versions

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify BIND 9 version
    Run 'named -v' or 'named -V' to obtain the installed BIND version number
    Affected if The version falls within 9.14.0 to 9.16.5, or 9.17.0 to 9.17.3
  2. Locate BIND configuration file
    Check /etc/named.conf or /etc/bind/named.conf for the named configuration file used by your installation
    Affected if A configuration file exists and BIND is in use
  3. Check if QNAME minimization is enabled
    Search the named.conf file for 'qname-minimization' or 'minimize-qname' directives and verify the setting is 'enabled' or 'yes'
    Affected if QNAME minimization is explicitly enabled in the configuration
  4. Check forwarder configuration
    Search the named.conf file within any 'options' or 'zone' blocks for 'forward' directive and verify if it is set to 'first'
    Affected if The forward option is set to 'first' (not 'only' or not present)

A server is affected only if it runs a vulnerable BIND 9 version (9.14.0-9.16.5 or 9.17.0-9.17.3) WITH both QNAME minimization enabled AND forward first configured. If forward is set to 'only' or either condition is absent, the server is not vulnerable to this CVE.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 2.2.2-5027 or later
Fixed in 2.2.2-5027
Interim mitigation

Disable QNAME minimization in the server configuration, change 'forward first' to 'forward only', or upgrade to BIND 9.16.6+, 9.17.4+, or a later stable version.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-8621 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data