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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2021.
Windows 10 1507Operating system · Microsoft

CVE-2021-34448

MEDIUM · 6.8 CVSS v3.1 Developing Published 2021-07-16
Fix available
A fix is available. Upgrade to 10.0.10240.19003 / 10.0.14393.4530 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Scripting Engine Memory Corruption Vulnerability

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-10.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 1507Operating system
Affected:< 10.0.10240.19003
Windows 10 1607Operating system
Affected:< 10.0.14393.4530
Windows 10 1809Operating system
Affected:< 10.0.17763.2061
Windows 10 1909Operating system
Affected:< 10.0.18363.1679
Windows 10 2004Operating system
Affected:< 10.0.19041.1110
Windows 10 20h2Operating system
Affected:< 10.0.19042.1110
Windows 10 21h1Operating system
Affected:< 10.0.19043.1110
Windows 7Operating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.10240.19003 / 10.0.14393.4530 / 10.0.17763.2061 or later
Fixed in 10.0.10240.1900310.0.14393.453010.0.17763.2061
Vendor patch portal.msrc.microsoft.com →
Recommended fix High confidence

Windows 10: upgrade to the June 2021 cumulative update (KB5003690) or later that meets the fixed build thresholds; Windows 7: migrate to Windows 10/11 or a supported operating system

  1. 1. Identify the current Windows version and build number by running 'winver' or 'systeminfo' in Command Prompt
  2. 2. Determine if the installed version is below the fixed build for your Windows 10 release (1507:10.0.10240.19003, 1607:10.0.14393.4530, 1809:10.0.17763.2061, 1909:10.0.18363.1679, 2004:10.0.19041.1110, 20h2:10.0.19042.1110, 21h1:10.0.19043.1110)
  3. 3. For Windows 7 (all versions): upgrade to a supported Windows version as Windows 7 is end-of-life with no security updates
  4. 4. For affected Windows 10 versions: apply the cumulative security update from Microsoft's June 2021 Patch Tuesday (KB5003690 or subsequent updates)
  5. 5. Verify the update installed successfully by checking the build number matches or exceeds the fixed version for your release
  6. 6. Restart the system as required by the security update
Caveat Windows 7 has reached end-of-life and has no security patches - migration to Windows 10/11 required; ensure application compatibility before updating Windows 10

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-34448 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data