CVE-2017-16119
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 · uneditedFresh is a module used by the Express.js framework for HTTP response freshness testing. It is vulnerable to a regular expression denial of service when it is 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 Fresh module, used by Express.js for HTTP response freshness testing, contains a vulnerable regular expression that can be exploited via specially crafted input. When parsed, this malformed input causes the regex to consume excessive computational resources, blocking the Node.js event loop and resulting in a denial of service condition.
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< 0.5.2CVSS 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 installed Fresh module versionRun 'npm list fresh' or 'npm list --depth=0' to see installed packages and their versionsAffected if The installed version of the fresh module is less than 0.5.2
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Check package.json for Fresh dependencyInspect your project's package.json file and look for 'fresh' in the dependencies or devDependencies sectionAffected if Fresh is listed with a version lower than 0.5.2 or with a range that resolves to an affected version (e.g., ^0.5.0, *, or ~0.5.1)
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Identify if Express.js uses FreshCheck your Express application code to see if it handles HTTP freshness checking via the 'fresh' module, typically through If-None-Match or If-Modified-Since request headersAffected if Your Express application processes HTTP requests with caching-related headers and relies on Express or the Fresh module for response freshness validation
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Verify vulnerability trigger conditionReview incoming HTTP requests to your application for patterns that could trigger the regex - specifically malformed input in If-None-Match or If-Modified-Since headersAffected if Your application accepts and processes HTTP requests with specially crafted values in freshness-checking headers that could be parsed by the vulnerable Fresh module regex
You are affected if the Fresh module version is below 0.5.2 AND your Express application processes HTTP requests with If-None-Match or If-Modified-Since headers that could trigger the vulnerable regex.
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 data0.5.2
Update the Fresh module to a patched version that addresses the ReDoS vulnerability. If immediate patching is not possible, implement rate limiting or input validation as a temporary mitigation to reduce the attack surface.
- Consultation2.0 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 $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-16119 — 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-2017-16119 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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