Threats / Google / CVE-2021-21220
CVE-2021-21220
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Google Chromium V8 vulnerability
Chromium V8 contains improper input validation allowing remote attackers to trigger heap corruption through crafted HTML, affecting multiple browsers including Chrome, Edge, and Opera.
Verdict
Today item — known-exploited.
A remote attacker can exploit this vulnerability by delivering a malicious HTML page to a victim's browser, potentially achieving code execution through heap memory corruption. Active exploitation in the wild increases risk.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
3 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 0.70435 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Google, Chromium V8. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation, CWE-122 Heap-based Buffer Overflow — 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 a malicious HTML page containing specially formed input that bypasses V8 validation checks.
Business
Users visiting attacker-controlled or compromised websites face immediate code execution risk without user interaction.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I trigger heap corruption in the V8 engine by providing input that violates expected memory boundaries.
Business
Browser process memory is compromised, enabling arbitrary code execution within the browser's security context.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute arbitrary code within the browser process to steal credentials, install malware, or pivot to system compromise.
Business
User devices and corporate networks face data theft, malware infection, and lateral movement threats.
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