CVE-2021-43437
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 · uneditedIn sourcecodetester Engineers Online Portal as of 10-21-21, an attacker can manipulate the Host header as seen by the web application and cause the application to behave in unexpected ways. Very often multiple websites are hosted on the same IP address. This is where the Host Header comes in. This header specifies which website should process the HTTP request. The web server uses the value of this header to dispatch the request to the specified website. Each website hosted on the same IP address is called a virtual host. And It's possible to send requests with arbitrary Host Headers to the first virtual host.
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 · moderate confidenceHost Header Injection vulnerability in sourcecodetester Engineers Online Portal allows attackers to manipulate the HTTP Host header to cause unexpected application behavior. The application likely uses the Host header value in sensitive operations (such as generating links, caching, or security decisions) without proper validation, allowing attackers to poison web caches, hijack password reset links, or conduct other attacks.
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= 1.0CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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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Identify Engineers Online Portal versionLocate the application files or check the about/admin page of the Engineers Online Portal. Look for version indicators in source files, README, or footer of pages.Affected if The installed version is exactly 1.0
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Inspect password reset functionalityExamine the source code files related to password reset (typically in a 'forgot_password.php' or similar file). Look for code that constructs reset links using $_SERVER['HTTP_HOST'] or similar Host header variables.Affected if The password reset code uses the Host header value to generate reset URLs without validation
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Check for Host header usage in link generationSearch source files for patterns like $_SERVER['HTTP_HOST'], $_SERVER['HOST'], or getHost() that are used to construct URLs, redirects, or links within the application.Affected if The application uses the Host header value to generate links or redirects without sanitization
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Test Host header behaviorSend an HTTP request to the application with a manipulated Host header (e.g., Host: evil.com) and observe whether the application reflects this value in generated URLs, redirects, or cached responses.Affected if The application accepts and uses the arbitrary Host header value in its response, generating links or redirects to the attacker-controlled domain
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Review application configurationCheck the application configuration files and server settings (like .htaccess, config.php, or web server config) for any whitelist-based Host header validation or security checks.Affected if No Host header whitelist validation is configured and the application does not sanitize Host header values before use
A user is affected if they are running Engineers Online Portal version 1.0 and the application uses the HTTP Host header in password reset links, URL generation, or caching decisions without proper validation.
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 dataImplement strict Host header validation using a whitelist of allowed values, avoid using the Host header in security-critical operations, and ensure the application validates the Host header against expected values before processing requests.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-43437 — 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-2021-43437 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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