CVE-2019-3635
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 · uneditedExfiltration of Data in McAfee Web Gateway (MWG) 7.8.2.x prior to 7.8.2.12 allows attackers to obtain sensitive data via crafting a complex webpage that will trigger the Web Gateway to block the user accessing an iframe.
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 confidenceIn McAfee Web Gateway versions 7.8.2.x prior to 7.8.2.12, an attacker can craft a malicious webpage containing an iframe designed to trigger MWG's blocking mechanism. When the Web Gateway blocks user access to this iframe, the blocking logic inadvertently exposes sensitive data that can be captured by the attacker, enabling data exfiltration.
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>= 7.8.2.0, < 7.8.2.12CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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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Determine McAfee Web Gateway versionLog into the MWG admin interface and navigate to Help > About, or run 'mwg-version' via CLI on the applianceAffected if The installed version is 7.8.2.x where x is less than 12 (versions 7.8.2.0 through 7.8.2.11)
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Confirm MWG is deployed as a proxy/gatewayCheck if the appliance is configured to intercept and filter HTTP/HTTPS traffic for clientsAffected if MWG is actively proxying or filtering web traffic, making it the point where iframe requests would be inspected and potentially blocked
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Verify web blocking rules are enabledIn the MWG admin console, navigate to Policy > Rules or Web Filtering settings and check if content blocking is turned onAffected if Content blocking or web filtering rules are enabled, particularly those that could match iframe elements in web pages
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Check if iframe blocking is in useReview the blocking policy rules to see if there are any rules that block or filter iframe elements, embed tags, or external content embeddingAffected if There are active rules that block iframe content or external object embedding, as this triggers the vulnerable blocking code path
You are affected if MWG version is 7.8.2.0 through 7.8.2.11 AND the appliance is actively blocking or filtering web content that includes iframes, enabling an attacker to exfiltrate data through the blocking response.
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 data7.8.2.12
Upgrade McAfee Web Gateway to version 7.8.2.12 or later to remediate the data exfiltration vulnerability in the iframe blocking logic.
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-3635 — 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-2019-3635 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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