CVE-2021-23856
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 web server is vulnerable to reflected XSS and therefore an attacker might be able to execute scripts on a client’s computer by sending the client a manipulated URL.
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 confidenceA reflected Cross-Site Scripting (XSS) vulnerability exists in the web server. Attackers can craft malicious URLs containing client-side scripts that are reflected back to users, potentially allowing execution of arbitrary JavaScript in the victim's browser when they click the manipulated link.
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 dataall versionsall versionsCVSS 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.
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Confirm product presenceIdentify if Bosch Rexroth Indramotion Mlc L20 or L40 controllers are deployed in your environment. Check system inventory, asset records, or physically verify the hardware model numbers.Affected if Either Indramotion Mlc L20 or L40 controller is present in your environment
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Verify web server is accessibleDetermine if the controller's web interface is network-accessible by attempting to reach the device IP or hostname on HTTP/HTTPS ports. Document which network segments can reach the web server.Affected if The web interface is reachable from any network segment where untrusted users could potentially operate
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Test for reflected input handlingSubmit a unique benign test string (such as a random alphanumeric sequence) as a URL parameter to the web server. Capture the HTTP response and check whether the test string is returned in the response body without encoding or sanitization.Affected if User-supplied input in URL parameters is reflected back in responses without proper encoding
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Inspect web server logsReview the Indramotion web server logs for entries containing script tags, JavaScript event handlers, or other XSS-related patterns in URL parameters that may indicate exploitation attempts.Affected if Logs contain evidence of XSS probing or reflected script content in requests
If Bosch Rexroth Indramotion Mlc L20 or L40 is present with an accessible web interface that reflects unencoded user input in URLs, the environment is affected by CVE-2021-23856.
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 proper input validation and output encoding for all user-supplied data, and configure Content Security Policy (CSP) headers to mitigate XSS attacks.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-23856 — 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-2021-23856 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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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