Sandbox escape via Portals use-after-free
Published Oct 8, 2021 · Updated Oct 21, 2025
Use-after-free in Portals in Google Chrome before 94.0.4606.61 allows remote attackers to escape the sandbox via crafted HTML. The Portals API can access memory after it has been freed when handling crafted page content, enabling corruption across the renderer boundary. Exploitation requires a previously compromised renderer process; Google reported the exploit in active campaigns, and the consequence is potential sandbox escape rather than guaranteed host compromise.
Summary
What happened
Use-after-free in Portals in Google Chrome before 94.0.4606.61 allows remote attackers to escape the sandbox via crafted HTML. The Portals API can access memory after it has been freed when handling crafted page content, enabling corruption across the renderer boundary. Exploitation requires a previously compromised renderer process; Google reported the exploit in active campaigns, and the consequence is potential sandbox escape rather than guaranteed host compromise.
The record
- CVE
- CVE-2021-37973
- Published
- Oct 8, 2021
- Updated
- Oct 21, 2025
- Vendor
- Google Cloud
- Product
- Google Chrome
- Classifications
- CWE-416, T1189
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 8, 2021CVE publishedPublication date reported by the CVE source.
- Nov 3, 2021Exploitation reportedCISA Known Exploited Vulnerability listing
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=unspecified <94.0.4606.61
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Reported exploitation
- CVE-2021-37973 exploited in the wildreported exploitation
- CISA Known Exploited Vulnerability listingknown exploited catalog
Technologies
Your stack
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Your stack
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