CVE-2021-21043
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 · uneditedACS Commons version 4.9.2 (and earlier) suffers from a Reflected Cross-site Scripting (XSS) vulnerability in version-compare and page-compare due to invalid JCR characters that are not handled correctly. An attacker could potentially exploit this vulnerability to inject malicious JavaScript content into vulnerable form fields and execute it within the context of the victim's browser. Exploitation of this issue requires user interaction in order to be successful.
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 confidenceReflected XSS vulnerability in ACS Commons versions 4.9.2 and earlier affecting the version-compare and page-compare components. The vulnerability stems from improper handling of invalid JCR characters, allowing attackers to inject malicious JavaScript that executes within the victim's browser session.
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<= 4.9.2CVSS 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
- 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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Identify ACS Commons bundle versionAccess the AEM Felix Console at /system/console/bundles and locate the 'ACS Commons' bundle. Check the Version column in the bundle list, or examine the bundle manifest file (org.apache.felix.framework) for the exported package versions.Affected if The installed version is 4.9.2 or lower.
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Locate ACS Commons package in package managerIn AEM Package Manager (/crx/packmgr), search for 'acs' or 'commons' packages. Check the package version listed in the package details for 'ACS Commons' or 'adobe-consulting-services-commons'.Affected if The installed package version is 4.9.2 or earlier.
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Verify version-compare component usageSearch the AEM content repository (using CRXDE Lite at /crx/de or the Query tool) for resources or components referencing 'version-compare' or the compare resource type path. Check if this component is actively used on any content pages.Affected if The version-compare component exists and is rendered in the environment.
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Verify page-compare component usageSearch the repository for resources referencing 'page-compare' or the page compare resource type path. Check if this compare functionality is accessible or deployed as a custom application component.Affected if The page-compare component exists and is accessible in the environment.
A user is affected if ACS Commons version 4.9.2 or earlier is installed AND either the version-compare or page-compare component is present and enabled in their AEM instance.
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 dataUpdate ACS Commons to version 4.9.3 or later to include the patch for proper JCR character sanitization. Alternatively, implement input validation and output encoding for JCR characters in the affected compare components.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21043 — 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-2021-21043 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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