Debian LinuxOperating system · Debian
CVE-2021-3468
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 avahi in versions 0.6 up to 0.8. The event used to signal the termination of the client connection on the avahi Unix socket is not correctly handled in the client_work function, allowing a local attacker to trigger an infinite loop. The highest threat from this vulnerability is to the availability of the avahi service, which becomes unresponsive after this flaw is triggered.
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 avahi versions 0.6 through 0.8 causes improper handling of the termination event signal for client connections on the Unix socket within the client_work function, leading to an infinite loop when triggered by a local attacker. This results in the avahi service becoming completely unresponsive, constituting a denial-of-service vulnerability.
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>= 0.6, <= 0.8CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 avahi is installedRun 'dpkg -l avahi-daemon' (Debian) or 'rpm -qa | grep avahi' (Red Hat) to see if the avahi package is presentAffected if avahi-daemon or avahi package is installed and the version is not known
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Determine the installed avahi versionRun 'avahi-daemon --version' or check with package manager: 'dpkg -s avahi-daemon' / 'rpm -q avahi-daemon'Affected if The version returned is 0.6, 0.7, or 0.8 (any version >= 0.6 and <= 0.8)
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Confirm the avahi-daemon service is runningRun 'systemctl status avahi-daemon' or 'service avahi-daemon status' to check if the daemon is activeAffected if The service is running - the vulnerability causes the daemon to become unresponsive when exploited
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Verify the Unix socket existsCheck for the avahi Unix socket at /var/run/avahi-daemon/socket or /run/avahi-daemon/socket using 'ls -la'Affected if The Unix socket is present - the flaw is triggered via client connections on this socket
You are affected if avahi-daemon version is 0.6, 0.7, or 0.8 and the service is running, since the vulnerability allows a local attacker to trigger an infinite loop via the Unix socket and cause denial of service.
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 avahi to version 0.8 or later, or apply vendor patches addressing the event handling logic in client_work to prevent the infinite loop condition.
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-2021-3468 — 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-2021-3468 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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