CVE-2026-43964
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 · uneditedPostfix before 3.8.16, 3.9 before 3.9.10, and 3.10 before 3.10.9 sometimes allows a buffer over-read and process crash via an enhanced status code that lacks text after the third number.
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 confidencePostfix SMTP server contains a buffer over-read vulnerability that can be triggered by specially crafted enhanced status code responses containing three numbers but missing the optional text portion after the third number. This causes the Postfix process to crash, resulting in denial of service.
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< 3.8.16>= 3.9.0, < 3.9.10>= 3.10.0, < 3.10.9CVSS 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 installed Postfix versionRun 'postconf mail_version' or 'postfix -v' to obtain the running Postfix versionAffected if Version is below 3.8.16, or between 3.9.0-3.9.9, or between 3.10.0-3.10.8
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Identify Postfix configuration file locationRun 'postconf -n' to display active configuration parametersAffected if Configuration is readable and contains enhanced status code settings
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Check for enhanced status code usageIn main.cf, search for 'smtpdEnhancedStatusCode' or 'smtpEnhancedStatusCode' parameters using 'postconf | grep EnhancedStatusCode'Affected if Either parameter is set to a value other than the default '0' (non-zero values enable enhanced status codes)
If the installed Postfix version falls within the affected ranges (before 3.8.16, 3.9.0-3.9.9, or 3.10.0-3.10.8) AND enhanced status codes are enabled (non-zero smtpdEnhancedStatusCode or smtpEnhancedStatusCode), the system is vulnerable to the buffer over-read crash.
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.
dbcve · scoped3.8.163.9.103.10.9
Upgrade Postfix to version 3.8.16, 3.9.10, or 3.10.9 or later to patch the buffer over-read vulnerability.
Postfix 3.8.16 (for 3.8.x), 3.9.10 (for 3.9.x), or 3.10.9 (for 3.10.x) - or latest stable release
- Check current Postfix version with: postconf -d mail_version
- Determine which major version branch you are currently running (3.8.x, 3.9.x, or 3.10.x)
- For systems on 3.8.x branch: upgrade to Postfix 3.8.16 or later
- For systems on 3.9.x branch: upgrade to Postfix 3.9.10 or later
- For systems on 3.10.x branch: upgrade to Postfix 3.10.9 or later
- On RHEL/RHEL-derived systems: run 'yum update postfix' or 'dnf update postfix'
- On Debian/Ubuntu systems: run 'apt-get update && apt-get install postfix'
- On source builds: download Postfix from http://www.postfix.org/ and rebuild
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-43964 — 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-2026-43964 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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- 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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