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CVE-2013-4073

MEDIUM · 6.8 CVSS v2.0 Published 2013-08-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
The OpenSSL::SSL.verify_certificate_identity function in lib/openssl/ssl.rb in Ruby 1.8 before 1.8.7-p374, 1.9 before 1.9.3-p448, and 2.0 before 2.0.0-p247 does not properly handle a '\0' character in a domain name in the Subject Alternative Name 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 confidence

The OpenSSL::SSL.verify_certificate_identity function in Ruby versions 1.8 before 1.8.7-p374, 1.9 before 1.9.3-p448, and 2.0 before 2.0.0-p247 fails to properly handle null byte ('\0') characters in domain names within the Subject Alternative Name field of X.509 certificates. This allows man-in-the-middle attackers to spoof legitimate SSL servers by using a crafted certificate containing a domain like 'target.com\0.malicious.com', causing Ruby to incorrectly validate the certificate as belonging to the trusted domain.

MitigationUpgrade Ruby to version 1.8.7-p374, 1.9.3-p448, 2.0.0-p247 or later. As a compensating control, implement additional certificate validation logic that strips or rejects domain names containing null bytes before trust evaluation.

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
RubyApplication
Affected:= 1.8.6-26= 1.8.7= 1.9.3= 2.0.0

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Ruby version
    Run 'ruby --version' or 'ruby -v' in the target environment
    Affected if The version is 1.8.x before 1.8.7-p374, 1.9.x before 1.9.3-p448, or 2.0.x before 2.0.0-p247
  2. Determine if OpenSSL SSL verification is in use
    Search Ruby codebases for calls to OpenSSL::SSL.verify_certificate_identity or SSL verification methods such as verify_certificate_identity, or inspect Ruby applications that perform HTTPS client connections using Ruby's net/http or OpenSSL library
    Affected if The application performs SSL/TLS certificate validation against domain names using Ruby's OpenSSL library
  3. Confirm if Subject Alternative Name validation occurs
    Inspect application code or SSL handshake logic to determine if certificate verification validates the Subject Alternative Name (SAN) field of X.509 certificates, as the vulnerability specifically affects SAN field processing
    Affected if The application validates certificate hostnames against the Subject Alternative Name field rather than only the Common Name field

A user is affected if they run an affected Ruby version (1.8.x before 1.8.7-p374, 1.9.x before 1.9.3-p448, or 2.0.x before 2.0.0-p247) and perform SSL certificate validation using the OpenSSL library's verify_certificate_identity function with domain names from the Subject Alternative Name field.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Ruby to version 1.8.7-p374, 1.9.3-p448, 2.0.0-p247 or later. As a compensating control, implement additional certificate validation logic that strips or rejects domain names containing null bytes before trust evaluation.

Fix this in Ruby Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing16.0 h
  • Review / QA4.0 h
38.0 hours of engineering $6,480
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2013-4073 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
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  • Version or environment caveats, and links to real fixes
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