Threats / Microsoft / CVE-2021-34448
CVE-2021-34448
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Windows vulnerability
Microsoft Windows Scripting Engine memory corruption vulnerability enabling arbitrary code execution through malicious scripts.
Verdict
Today item — known-exploited.
Out-of-bounds write in scripting engine allows attackers to corrupt memory and achieve code execution. Active exploitation observed in the wild. Affects Windows systems running vulnerable scripting components.
CISA KEV Yes · 2021-11-035EPSS 0.3067 (verify live)6CVSS 6.83CISA SSVC Exploitation: active · Automatable: yes · Impact: total4
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 0.3067 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C) · Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-787 Out-of-bounds Write — 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: yes · 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 110 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
Craft malicious script that triggers out-of-bounds memory write in scripting engine
Business
Attacker gains arbitrary code execution on victim Windows system
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
Deliver script via email, web, or document embedding to target users
Business
Compromise spreads to user endpoints and potentially internal network
3
Lateral reach — past segmentation narrative 3
Attacker
Execute payload with privileges of compromised user account
Business
Data exfiltration, lateral movement, or persistence established on enterprise systems
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