ChromeWeb browser · Google
CVE-2026-9903
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 · uneditedInsufficient validation of untrusted input in Site Isolation in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted MHTML page. (Chromium security severity: High)
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 confidenceInsufficient validation of untrusted input in Chrome's Site Isolation feature allowed a remote attacker who had already compromised the renderer process to bypass site isolation protections via a crafted MHTML page. This could enable the attacker to access data from other origins that should be isolated.
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
ChromeWeb browser
< 148.0.7778.216CVSS 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
- High
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L
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 installed Chrome versionOpen chrome://version in the Chrome address bar and note the version number displayed under 'Google Chrome' (first line), or go to Help > About Google ChromeAffected if The version number is less than 148.0.7778.216 (for example, 148.0.7778.0, 147.x.x.x, etc.)
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Confirm version comparisonCompare your installed version string against the affected range: any version before 148.0.7778.216 is vulnerable; version 148.0.7778.216 and later are notAffected if Your installed version falls below 148.0.7778.216
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Verify Site Isolation status (optional context)Navigate to chrome://site-isolation in the address bar to confirm Site Isolation is enabled; note that this feature is enabled by default in modern Chrome versionsAffected if Site Isolation is disabled AND your Chrome version is below 148.0.7778.216 (though the version check alone is sufficient for detection)
You are affected if your Google Chrome version is lower than 148.0.7778.216, since the vulnerability exists in the Site Isolation mechanism of those earlier versions.
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.
dbcve · scoped148.0.7778.216
Update Google Chrome to version 148.0.7778.216 or later. Organizations should ensure standard browser patch management processes are in place and verify the Chrome version across managed endpoints.
Chrome 148.0.7778.216 or later
- 1. Open Google Chrome on your system
- 2. Navigate to Chrome menu > Help > About Google Chrome
- 3. The browser will automatically check for updates
- 4. If an update is available, download and install it
- 5. Restart Chrome to complete the update
- 6. Verify the version by going to chrome://settings/help - it should show 148.0.7778.216 or later
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Chrome
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 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 $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9903 — 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-2026-9903 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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