Vulnerability report

Exploitation attempts observed in the wild Confirmed confidence In CISA KEV

CVE-2021-34448

Scripting Engine Memory Corruption Vulnerability

Microsoft / Windows 10 Version 1507 · affected before 10.0.10240.19003

Watch CVE-2021-34448 Browse KEV feed
Severity
CVSS 6.8 · Medium
Confidence
Confirmed
Exploit status
Exploitation attempts observed in the wild
EPSS
40.1%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-34448 is an unauthenticated Scripting Engine Memory Corruption Vulnerability affecting Microsoft Windows 10 Version 1507 and 14 other products.

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

Microsoft / Windows 10 Version 1507 affected before 10.0.10240.19003.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Scripting Engine Memory Corruption Vulnerability

Scripting Engine Memory Corruption Vulnerability

Microsoft Affected
Windows 10 Version 1507
Before 10.0.10240.19003
Microsoft Affected
Windows 10 Version 1607
Before 10.0.14393.4530
Microsoft Affected
Windows 10 Version 1809
Before 10.0.17763.2061
Microsoft Affected
Windows 10 Version 1909
Before 10.0.18363.1679
Microsoft Affected
Windows 10 Version 2004
Before 10.0.19041.1110
Microsoft Affected
Windows 10 Version 20H2
Before 10.0.19042.1110
Microsoft Affected
Windows 10 Version 21H1
Before 10.0.19043.1110
Microsoft Affected
Windows 7
Before 6.1.7601.25661
Microsoft Affected
Windows 7 Service Pack 1
Before 6.1.7601.25661
Microsoft Affected
Windows 8.1
Before 6.3.9600.20069
Microsoft Affected
Windows Server 2008 R2 Service Pack 1
Before 6.1.7601.25661
Microsoft Affected
Windows Server 2012
Before 6.2.9200.23409
Microsoft Affected
Windows Server 2012 R2
Before 6.3.9600.20069
Microsoft Affected
Windows Server 2016
Before 10.0.14393.4530
Microsoft Affected
Windows Server 2019
Before 10.0.17763.2061
View vendor advisory (opens in new tab)
Published
16 Jul 2021
Exploitation Attempts Reported
03 Nov 2021
Attack vector
Remote
Complexity
High
Privileges
None
User interaction
Required

Tags

microsoft windows cisa

CVE References

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation attempts observed in the wild

CISA

Recorded 03 Nov 2021

A trusted third party reported exploitation attempts.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CISA First 2021-11-03 00:00 UTC
CVE 2026-08-10 15:31 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

6.8 Medium

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

40.1%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Out-of-bounds Write CWE-787

All CVSS Scores

CVSS v3.1 6.8 Medium

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

CVSS v2.0 9.3 High

AV:N/AC:M/Au:N/C:C/I:C/A:C

Timeline

From disclosure to observed exploitation attempts

  1. 15:31 UTC

    KEV confirmed by CVE

    Exploitation attempts reported by an external source

  2. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  3. 20:19 UTC

    CVE published

    Vulnerability disclosed publicly

  4. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-34448

Sample API response 
{
  "cve_id": "CVE-2021-34448",
  "confidence": "Confirmed",
  "cvss_score": 6.8,
  "cvss_estimated": false,
  "epss_score": 0.40062,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}