CVE-2021-30633: Google Chromium Indexed DB API Use-After-Free Vulnerability

CVE-2021-30633 is a use-after-free vulnerability in the Google Chromium Indexed DB API. A remote attacker who has already compromised the renderer process can potentially escape the browser sandbox by means of a crafted HTML page. Because many browsers are built on Chromium, the issue can affect Google Chrome, Microsoft Edge, Opera, and other Chromium-based products. Teams should treat it as a high-priority browser risk and confirm exact impact and fixes against the vendor advisory.

How it works

The weakness is classified as CWE-416 (use-after-free). In this class of flaw, memory is freed while a pointer to it remains in use; subsequent access can corrupt memory or allow unintended code paths. Per the CISA summary, an attacker who has already compromised the renderer process can abuse the Indexed DB API path with a crafted HTML page to attempt a sandbox escape. Public detail does not describe the precise memory objects or trigger sequence; defenders should treat any successful renderer compromise combined with malicious web content as a potential path to broader browser process control and should verify technical specifics only in the vendor advisory.

Am I affected? How to find it in your systems

Chromium-based browsers are common on endpoints, VDI images, kiosks, and developer workstations. Inventory every browser that embeds Chromium—Google Chrome, Microsoft Edge, Opera, and any other Chromium derivative—across managed and unmanaged devices.

• Query software inventory, MDM/EMM, or package managers for installed browser products and build versions; compare them to the fixed versions listed in each vendor’s advisory for CVE-2021-30633.
• Check enterprise browser management policies and extension catalogs that may pin older Chromium engines.
• Review whether users routinely open untrusted or internet-sourced HTML content, which is the delivery vehicle described for this issue.
• Telemetry signs of exploitation are not detailed in the provided facts; look generally for unexpected renderer or browser-process crashes, sandbox violations, or anomalous child-process creation after navigation to untrusted pages, and correlate with vendor guidance.

If version or configuration data is unclear, assume potential exposure until you confirm against the vendor advisory.

How to remediate

Patch first. Apply the updates issued by each browser vendor exactly as directed in their advisories; CISA’s required action is to apply updates per vendor instructions. After patching:

• Force browser restarts or redeploy updated packages so the fixed Chromium components are loaded.
• Re-scan inventory to verify no residual vulnerable builds remain on endpoints or golden images.
• For this vulnerability class, keep automatic browser updates enabled where policy allows, restrict unnecessary access to local file or extension APIs, and maintain least-privilege user accounts so a sandbox escape has limited follow-on value.
• Retire or isolate any legacy Chromium-based applications that cannot be updated.

If you can't patch immediately

Reduce exposure until updates can be deployed:

• Segment high-risk browsing (untrusted sites, email links) onto isolated VDI or dedicated browsing hosts that do not hold sensitive credentials or data.
• Use enterprise browser controls or content filters to block or warn on untrusted HTML/JavaScript where feasible; virtual patching via WAF or secure web gateway may help only for browser-based enterprise web apps, not for general endpoint browsing.
• Disable or limit features that increase renderer attack surface if your browser management tools allow it, and confirm any such change against vendor documentation so you do not break required functionality.
• Heighten monitoring for browser process anomalies, crash storms, and unusual outbound connections from browser child processes; capture memory or crash dumps for later analysis if exploitation is suspected.
• Prioritize patching of internet-facing and high-privilege user populations first.

If your data may have been exposed

Actively exploited browser sandbox-escape vulnerabilities can lead to further compromise of the endpoint and potential data exposure. Known ransomware use of this CVE is not documented in the provided facts. If you suspect exploitation, follow your incident-response process: isolate affected hosts, preserve evidence, rotate credentials that may have been accessible from the browser session, and assess lateral movement. You can run a free exposure scan of your email addresses against known breach data to check whether associated credentials or personal data have appeared in prior breaches while you complete containment and recovery.