CVE-2025-21201
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 · uneditedWindows Telephony Server Remote Code Execution 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 analysisThe same block of memory is freed twice, corrupting the allocator's bookkeeping in ways an attacker can shape toward code execution. It usually stems from tangled ownership of a pointer. The fix is clear, single ownership of each allocation and clearing pointers once they are freed.
General guidance for the double free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
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< 10.0.10240.20915< 10.0.14393.7785< 10.0.17763.6893< 10.0.19044.5487< 10.0.19045.5487< 10.0.22621.4890< 10.0.22631.4890< 10.0.26100.3194CVSS 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
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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 · scoped10.0.10240.2091510.0.14393.778510.0.17763.6893
Upgrade to the latest Windows Security Update containing the CVE-2025-21201 patch, reaching the minimum build number for your respective Windows version as listed above
- Identify the current Windows version by running 'winver' or 'systeminfo' from Command Prompt
- Determine which Windows 10 or 11 version and build is installed (e.g., 22h2, 23h2, 24h2)
- Apply the appropriate Windows Security Update for CVE-2025-21201 via Windows Update (Settings > Update & Security > Windows Update > Check for updates), or manually download the update from the Microsoft Update Catalog
- Verify the installation was successful by checking that the build number matches or exceeds: Windows 10 1507: 10.0.10240.20915, Windows 10 1607: 10.0.14393.7785, Windows 10 1809: 10.0.17763.6893, Windows 10 21h2: 10.0.19044.5487, Windows 10 22h2: 10.0.19045.5487, Windows 11 22h2: 10.0.22621.4890, Windows 11 23h2: 10.0.22631.4890, Windows 11 24h2: 10.0.26100.3194
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-21201 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-21201 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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