CVE-2021-38084
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 · uneditedAn issue was discovered in the POP3 component of Courier Mail Server before 1.1.5. Meddler-in-the-middle attackers can pipeline commands after the POP3 STLS command, injecting plaintext commands into an encrypted user session.
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 MITM vulnerability in Courier Mail Server's POP3 component allows attackers to inject plaintext commands after the STLS command but before the TLS handshake completes, potentially hijacking the encrypted session. The server fails to properly isolate commands sent during the STLS transition, enabling command injection into what should be an encrypted connection.
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< 1.1.5CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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.
-
Identify Courier Mail Server installationCheck for Courier MTA or Courier Mail Server packages using your system package manager (dpkg, rpm, pkg) or by locating binaries such as /usr/sbin/courier or /usr/bin/courierdAffected if Courier Mail Server is not installed
-
Determine installed versionRun 'courierd --version' or check the package version via your package manager (dpkg -l courier-mta or rpm -qi courier-mta)Affected if Version is present but below 1.1.5
-
Verify POP3 service is enabledCheck for POP3 daemon process (courierpop3d) or examine init/systemd service files, or check /etc/courier/pop3d configurationAffected if POP3 service is not running or not configured
-
Confirm STLS capability is availableExamine /etc/courier/pop3d-ssl or related SSL configuration files for STLS enablement, or connect to POP3 port (110) and issue the STLS command to verify the server accepts itAffected if STLS command is accepted by the POP3 server
If Courier Mail Server version is below 1.1.5 AND POP3 with STLS is enabled, the environment is vulnerable to this CVE.
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 data1.1.5
Upgrade to Courier Mail Server 1.1.5 or later which contains the fix for proper STLS command sequencing. Until then, ensure POP3 traffic is not routed through untrusted networks where MITM is possible.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 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 $4,512.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-38084 — 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-2021-38084 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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