Ubuntu LinuxOperating system · Canonical
CVE-2020-8620
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 · uneditedIn BIND 9.15.6 -> 9.16.5, 9.17.0 -> 9.17.3, An attacker who can establish a TCP connection with the server and send data on that connection can exploit this to trigger the assertion failure, causing the server to exit.
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 · moderate confidenceA remote denial-of-service vulnerability in BIND 9 DNS server (versions 9.15.6-9.16.5 and 9.17.0-9.17.3) where an unauthenticated attacker who can establish a TCP connection and send data can trigger an assertion failure, causing the DNS server to crash.
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
= 12.04= 16.04= 18.04>= 9.15.6, <= 9.16.5>= 9.17.0, <= 9.17.3= 9.9.12= 9.9.13= 9.11.3= 9.11.21= 15.1= 15.2all versionsCVSS 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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Check if BIND 9 is installedRun `named -v` or `bind -v` to display the BIND version, or use your package manager (dpkg -l | grep bind, rpm -qa | grep bind)Affected if BIND 9 is present on the system
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Verify the installed BIND version against affected rangesCompare the version output from the previous step to the affected versions: 9.15.6 through 9.16.5, 9.17.0 through 9.17.3, or specifically 9.9.12, 9.9.13, 9.11.3, 9.11.21Affected if The installed version falls within any of these ranges
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Confirm TCP is enabled in BIND configurationInspect the named.conf file (typically in /etc/bind/named.conf or /etc/named.conf) and look for the `tcp-clients` directive or check if `listen-on` includes TCP port 53Affected if TCP is enabled (tcp-clients is not set to 0 or listen-on includes TCP)
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Check if the DNS server is network accessibleRun `netstat -tlnp | grep :53` or `ss -tlnp | grep :53` to see if named is listening on TCP port 53 on a network interfaceAffected if The server is listening on TCP port 53 on a non-loopback interface
You are affected if BIND 9 is running with a version in the ranges 9.15.6-9.16.5, 9.17.0-9.17.3, or the specific older versions 9.9.12, 9.9.13, 9.11.3, 9.11.21, and TCP is enabled with the server exposed to network access.
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 BIND 9 to version 9.16.6, 9.17.4, or later. If immediate patching is not feasible, consider restricting TCP access to authorized resolvers via firewall rules or ACLs.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8620 — 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-2020-8620 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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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.
- 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
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