Threats / Google / CVE-2021-37973
CVE-2021-37973
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Google Chromium Portals vulnerability
Use-after-free vulnerability in Google Chromium Portals allows a compromised renderer process to escape the sandbox via crafted HTML, affecting Chrome and Edge browsers.
Verdict
Today item — known-exploited.
A remote attacker who has already compromised the renderer process can exploit this use-after-free to potentially escape the browser sandbox. Active exploitation in the wild has been observed.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
6 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.11735 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Google, Chromium Portals. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-416 Use After Free — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft malicious HTML that triggers a use-after-free condition in the Portals implementation.
Business
User visits attacker-controlled or compromised website, initiating the attack chain.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the use-after-free to gain code execution within the renderer process.
Business
Attacker gains ability to read sensitive data from the renderer and bypass same-origin policies.
3
Lateral reach — past segmentation narrative 3
Attacker
I leverage renderer code execution to escape the sandbox and access the host system.
Business
System compromise becomes possible, enabling malware installation, credential theft, or lateral movement.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05