Threats / Google / CVE-2021-21148
CVE-2021-21148
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Google Chromium V8 vulnerability
Heap buffer overflow in Chromium V8 engine allows remote code execution through crafted HTML pages, affecting Chrome, Edge, and other Chromium-based browsers.
Verdict
Today item — known-exploited.
Remote attacker can trigger heap corruption via malicious web content, potentially achieving code execution in the context of the affected browser process.
CISA KEV Yes · 2021-11-034EPSS 0.19815 (verify live)5CVSS 8.8 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: total3
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 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 0.19815 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 8.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) · Affected: Google, Chromium V8. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-122 Heap-based Buffer Overflow — weakness family: Memory safety.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 267 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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 that triggers a heap buffer overflow in the V8 JavaScript engine.
Business
User visits attacker-controlled or compromised website and browser process is compromised.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the heap corruption to achieve arbitrary code execution within the browser sandbox.
Business
Attacker gains ability to execute code with browser process privileges, potentially accessing user data.
3
Lateral reach — past segmentation narrative 3
Attacker
I use the code execution to steal credentials, session tokens, or sensitive information from the compromised browser.
Business
User accounts, financial data, or personal information may be compromised across multiple services.
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