CVE-2016-6286
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 · uneditedThe "spiffy-cgi-handlers" egg would convert a nonexistent "Proxy" header to the HTTP_PROXY environment variable, which would allow attackers to direct CGI programs which use this environment variable to use an attacker-specified HTTP proxy server (also known as a "httpoxy" attack). This affects all versions of spiffy-cgi-handlers before 0.5.
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 confidenceThe spiffy-cgi-handlers Common Lisp library improperly forwarded the HTTP 'Proxy' request header as the HTTP_PROXY environment variable to CGI programs. Since CGI applications commonly use HTTP_PROXY to configure proxy behavior, an attacker sending a malicious 'Proxy' header could redirect the application's outbound HTTP traffic through an attacker-controlled proxy server, enabling MITM attacks and request interception (httpoxy vulnerability).
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<= 0.4.2CVSS 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
- High
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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 installed version of Call Cc Http ClientRun the package manager or lisp system to query the installed version of Call Cc Http Client (e.g., (ql:quickload :call-cc-http-client) and check *version* or similar, or check your project's quicklisp/local-projects directory for the library)Affected if The installed version is 0.4.2 or lower
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Confirm CGI handler functionality is in useInspect your application code or configuration to determine if spiffy-cgi-handlers is loaded and used to handle CGI requestsAffected if Your application uses spiffy-cgi-handlers to process CGI requests
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Verify Proxy header forwarding behaviorExamine the spiffy-cgi-handlers source code or configuration to confirm it forwards incoming HTTP headers to CGI environment variables, particularly checking for code that maps the Proxy header to HTTP_PROXYAffected if The library forwards the Proxy header as HTTP_PROXY environment variable to CGI programs
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Test for environment variable injectionSend a request with a 'Proxy:' header to your CGI application and inspect the CGI environment (e.g., check if HTTP_PROXY is set to the attacker-supplied value)Affected if The Proxy header value from incoming requests appears as HTTP_PROXY in the CGI environment
You are affected if you run Call Cc Http Client version 0.4.2 or lower and use spiffy-cgi-handlers to serve CGI applications, as the library will forward attacker-controlled Proxy headers as HTTP_PROXY environment variables.
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 spiffy-cgi-handlers to version 0.5 or later, which blocks the Proxy header from being passed to the CGI environment. Audit all CGI applications using this library to confirm they are not vulnerable to proxy redirection.
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2016-6286 — 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-2016-6286 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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- Version or environment caveats, and links to real fixes
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