CVE-2009-3765
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 · uneditedmutt_ssl.c in mutt 1.5.19 and 1.5.20, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
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 confidenceMutt email client versions 1.5.19 and 1.5.20 fail to properly validate X.509 certificates when OpenSSL is used. The vulnerability allows a null character ('\0') embedded in the certificate's Common Name (CN) field to act as a string terminator, causing the client to accept the certificate for a different domain than intended. This enables man-in-the-middle attackers to spoof legitimate SSL servers using certificates issued by trusted Certification Authorities.
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= 1.5.19= 1.5.20CVSS 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
- M
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:M/Au:N/C:P/I:P/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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Determine installed Mutt versionRun 'mutt -v' or 'mutt --version' to see the installed version numberAffected if The version shown is exactly 1.5.19 or 1.5.20
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Confirm SSL/TLS support is enabledCheck the mutt configuration file (typically ~/.muttrc or /etc/Muttrc) for SSL-related settings such as 'set ssl_force_tls', 'set smtp_ssl_force_tls', 'set pop_ssl_force_tls', or 'set imap_ssl_force_tls'Affected if SSL or TLS is configured for any protocol (SMTP, POP3, or IMAP) - the vulnerability applies when OpenSSL is used for secure connections
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Verify OpenSSL is the crypto backendRun 'mutt -v' and look for 'OpenSSL' in the compiled-in features or crypto capabilitiesAffected if OpenSSL is listed as the SSL/TLS backend - the vulnerability exists specifically when Mutt is linked against OpenSSL
You are affected if your installed Mutt version is exactly 1.5.19 or 1.5.20 AND you have SSL/TLS connections enabled using OpenSSL.
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 mutt version 1.5.21 or later which contains the fix for proper CN field validation. Alternatively, if upgrading is not possible, verify certificate fingerprints manually before accepting connections to sensitive servers.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 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 $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-3765 — 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-2009-3765 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
- No spam, self-promotion, credentials, or personal data