CVE-2021-20101
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 · uneditedMachform prior to version 16 is vulnerable to HTTP host header injection due to improperly validated host headers. This could cause a victim to receive malformed content.
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 confidenceMachform prior to version 16 is vulnerable to HTTP host header injection due to improperly validated host headers. The application does not properly sanitize or validate the Host header value supplied in HTTP requests, which could allow an attacker to manipulate the content delivered to victims by injecting malicious host values.
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< 16CVSS 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
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/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.
-
Locate Machform installationSearch for Machform directories or files on the web server. Common paths include /machform, /form, or similar. Check web server configuration for Machform virtual hosts or document roots.Affected if Machform is not installed on the server
-
Identify Machform version numberLook for a version file or check the main PHP files for a version constant. Common locations include: version.php, includes/version.php, or the main index.php file often contains version information in comments or defined constants.Affected if Unable to determine the installed version
-
Compare version against affected rangeParse the identified version number and compare it to version 16. Versions prior to 16 (e.g., 15.x, 14.x, etc.) are affected. Versions 16.0 and later are not affected.Affected if The installed Machform version is less than 16 (e.g., 15.x, 14.x, 13.x)
-
Inspect Host header processing (optional)Review application configuration files and PHP code to confirm the application processes and uses the HTTP Host header in any functionality such as email links, form submissions, or URL generation.Affected if The application uses the Host header in generated content or links (required for exploitation)
The environment is affected only if Machform is installed and its version is prior to 16.
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 data16
Upgrade to Machform version 16 or later. Additionally, implement explicit host header validation to reject unexpected host values at the web server or application level.
- Consultation2.0 h
- Implementation3.0 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 $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20101 — 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-2021-20101 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data