CVE-1999-1109
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 · uneditedSendmail before 8.10.0 allows remote attackers to cause a denial of service by sending a series of ETRN commands then disconnecting from the server, while Sendmail continues to process the commands after the connection has been terminated.
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 confidenceSendmail versions before 8.10.0 contain a denial-of-service vulnerability where the server continues processing ETRN commands after the client has disconnected. Attackers can exploit this by sending multiple ETRN commands followed by an immediate disconnect, causing Sendmail to waste resources on abandoned connections.
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<= 8.10.0CVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 if Sendmail is runningCheck for running sendmail processes: ps aux | grep -i sendmail or systemctl status sendmailAffected if No sendmail process is found, the system is not affected by this vulnerability
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Determine the installed Sendmail versionRun 'sendmail -V' or 'sendmail -d0.1' to display the version numberAffected if The version number displayed is 8.10.0 or lower (for example 8.9.x, 8.8.x, etc.)
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Verify ETRN command availabilityConnect to the SMTP port (25) and issue the ETRN command by typing 'ETRN test' and observing the responseAffected if The server accepts and processes the ETRN command, indicating the feature is enabled
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Check SMTP service exposureReview firewall rules (iptables -L -n) or network configuration to determine if port 25 is accessible from external network sourcesAffected if Port 25 is exposed to untrusted networks, increasing the attack surface for this vulnerability
A system is affected if it runs Sendmail version 8.10.0 or earlier with the ETRN command enabled and port 25 accessible to potential attackers.
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 to Sendmail 8.10.0 or later, or migrate to a modern mail server solution. If legacy Sendmail systems must remain in service, implement connection timeout limits and rate limiting on the SMTP service.
- Consultation1.0 h
- Implementation8.0 h
- Testing2.0 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 $3,392.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-1999-1109 — 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-1999-1109 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
- No spam, self-promotion, credentials, or personal data