NVD / CVE Program· CNA microsoft

CVE-2023-21543: Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability

HighCVSS 8.1 · v3.1—No exploit No fix recorded

Noroxi assessment

Priority: Monitor (action score 33/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 1.6% (FIRST EPSS); higher than 77% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

BDU:2023-00138

Published: Jan 10, 2023
Updated: Jun 17, 2026
EPSS: 1.6% · 77th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 32 / 40 · 8.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 1.6%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · microsoft: 8.1; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
microsoft	windows 10 1607	cpe:2.3:o:microsoft:windows_10_1607
microsoft	windows 10 1809	cpe:2.3:o:microsoft:windows_10_1809
microsoft	windows 10 20h2	cpe:2.3:o:microsoft:windows_10_20h2
microsoft	windows 10 21h2	cpe:2.3:o:microsoft:windows_10_21h2
microsoft	windows 10 22h2	cpe:2.3:o:microsoft:windows_10_22h2
microsoft	windows 11 21h2	cpe:2.3:o:microsoft:windows_11_21h2
microsoft	windows 11 22h2	cpe:2.3:o:microsoft:windows_11_22h2
microsoft	windows 7	cpe:2.3:o:microsoft:windows_7
microsoft	windows 8.1	cpe:2.3:o:microsoft:windows_8.1
microsoft	windows rt 8.1	cpe:2.3:o:microsoft:windows_rt_8.1
microsoft	windows server 2008	cpe:2.3:o:microsoft:windows_server_2008
microsoft	windows server 2012	cpe:2.3:o:microsoft:windows_server_2012

and 3 more

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

Microsoft Windows 10 Version 1507
- 10.0.10240.0 and later · before 10.0.10240.19685affected
Microsoft Windows 10 Version 1607
- 10.0.14393.0 and later · before 10.0.14393.5648affected
Microsoft Windows 10 Version 1809
- 10.0.17763.0 and later · before 10.0.17763.3887affected
- 10.0.0 and later · before 10.0.17763.3887affected
Microsoft Windows 10 Version 20H2
- 10.0.0 and later · before 10.0.19042.2486affected
Microsoft Windows 10 Version 21H2
- 10.0.19043.0 and later · before 10.0.19044.2486affected
Microsoft Windows 10 Version 22H2
- 10.0.19045.0 and later · before 10.0.19045.2486affected
Microsoft Windows 11 version 21H2
- 10.0.0 and later · before 10.0.22000.1455affected
Microsoft Windows 11 version 22H2
- 10.0.22621.0 and later · before 10.0.22621.1105affected
Microsoft Windows 7
- 6.1.0 and later · before 6.1.7601.26321affected
Microsoft Windows 7 Service Pack 1
- 6.1.0 and later · before 6.1.7601.26321affected
Microsoft Windows 8.1
- 6.3.0 and later · before 6.3.9600.20778affected
Microsoft Windows Server 2008 Service Pack 2
- 6.0.6003.0 and later · before 6.0.6003.21872affected

Affected versions · NVD (7)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

microsoft windows server 2008all versions
microsoft windows server 2008r2
microsoft windows server 2012all versions
microsoft windows server 2012r2
microsoft windows server 2016all versions
microsoft windows server 2019all versions
microsoft windows server 2022all versions

Same product

microsoft: all records

Other highest-scoring records for the same primary product.

CVE-2026-33824Windows Internet Key Exchange (IKE) Service Extensions Remote Code Execution VulnerabilityKEV
92Now
CVE-2018-8174A remote code execution vulnerability exists in the way that the VBScript engine handles objects in memory, aka "Windows VBScript Engine…KEV
86Now
CVE-2026-21510Windows Shell Security Feature Bypass VulnerabilityKEV
83Now

Published before and after this one in the same product

← EarlierCVE-2023-21541Jan 10, 2023 · Windows Task Scheduler Elevation of Privilege Vulnerability
31Monitor
← EarlierCVE-2023-21542Jan 10, 2023 · Windows Installer Elevation of Privilege Vulnerability
28Monitor
Later →CVE-2023-21546Jan 10, 2023 · Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability
32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log (0)

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21543

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records