CVE-2017-16118
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 forwarded module is used by the Express.js framework to handle the X-Forwarded-For header. It is vulnerable to a regular expression denial of service when it's passed specially crafted input to parse. This causes the event loop to be blocked causing a denial of service condition.
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 'forwarded' npm module used by Express.js to parse X-Forwarded-For headers is vulnerable to a regular expression denial of service (ReDoS) attack. Specially crafted input to the parser causes the regex engine to take excessively long processing time, blocking the Node.js event loop and causing 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< 0.1.2CVSS 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
- None
- Availability
- High
CVSS:3.0/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 if the forwarded module is installedRun 'npm list forwarded' in your project directory to see if the forwarded package is listed as a dependencyAffected if The forwarded package appears in the dependency tree
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Determine the installed version of forwardedRun 'npm list forwarded version' or check your package-lock.json file for the 'forwarded' package version numberAffected if The version number is less than 0.1.2 (e.g., 0.1.1, 0.1.0, etc.)
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Check if Express.js uses the forwarded moduleRun 'npm list express' and 'npm why forwarded' to confirm that Express depends on the forwarded package, or inspect the express package.json dependenciesAffected if Express.js is using the vulnerable forwarded module as a dependency
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Verify X-Forwarded-For header parsing is in useInspect your application code for usage of Express 'trust proxy' setting or direct use of the forwarded module to parse X-Forwarded-For headersAffected if Your application configures Express trust proxy settings or explicitly parses X-Forwarded-For headers, enabling the vulnerable code path
Your environment is affected if the forwarded module version is below 0.1.2 AND your application uses Express with proxy trust settings or parses X-Forwarded-For headers.
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 data0.1.2
Update the 'forwarded' module to a patched version that addresses the ReDoS vulnerability. Alternatively, upgrade Express.js to a version that includes the patched dependency.
- Consultation1.0 h
- Implementation1.0 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 $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-16118 — 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-2017-16118 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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