CVE-2020-5404
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 HttpClient from Reactor Netty, versions 0.9.x prior to 0.9.5, and versions 0.8.x prior to 0.8.16, may be used incorrectly, leading to a credentials leak during a redirect to a different domain. In order for this to happen, the HttpClient must have been explicitly configured to follow redirects.
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 HttpClient in Reactor Netty versions 0.8.x prior to 0.8.16 and 0.9.x prior to 0.9.5 leaks credentials when following redirects to a different domain. When the client is explicitly configured to follow redirects, sensitive authorization headers or cookies may be sent to the redirect target domain, violating same-origin security expectations.
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>= 0.8.0, <= 0.8.15>= 0.9.0, <= 0.9.4CVSS 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
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/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 Reactor Netty dependencyInspect your project's dependency management file (pom.xml, build.gradle, package.json, or similar) for the reactor-netty artifactAffected if reactor-netty is present as a dependency
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Determine Reactor Netty versionCheck the resolved version of reactor-netty in your dependency tree or build output. Compare against affected ranges: 0.8.0-0.8.15 or 0.9.0-0.9.4Affected if installed version falls within 0.8.0 through 0.8.15, or 0.9.0 through 0.9.4
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Verify HttpClient redirect configurationSearch codebase for HttpClient instantiation with redirect following enabled, typically via .followRedirect(true) or similar redirect configuration methodAffected if HttpClient is explicitly configured to follow redirects
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Confirm authentication in use with redirect-following clientReview HttpClient usage to determine if authorization headers, cookies, or other credentials are sent with requests while redirect following is enabledAffected if authentication headers or cookies are transmitted via an HttpClient that follows redirects
Environment is affected if using Reactor Netty 0.8.0-0.8.15 or 0.9.0-0.9.4 with an HttpClient configured to follow redirects while sending sensitive authorization headers or cookies.
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 Reactor Netty to version 0.8.16+ or 0.9.5+. If immediate upgrade is not feasible, avoid configuring HttpClient to follow redirects when handling authenticated requests to mitigate credential exposure.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-5404 — 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-2020-5404 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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