Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 1.10% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2023
CVE-2023-21555High confidence
Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability
Microsoft · Windows 10 Version 1809
8.1HighCVSS 3.1
Within 7 days
Fix not verifiedHigh technical severity; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Microsoft Windows 10 Version 1809 and falls inside the recorded affected range.
- Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Fix not verified01
What, why and how
Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability
What
Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability
Why
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
What
Windows Layer 2 Tunneling Protocol (L2TP) Remote Code Execution Vulnerability
Why
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Time-of-check Time-of-use (TOCTOU) Race Condition → execute code or commands in the affected security context
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-367 ↗
CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix not verified
- Affected
- Windows 10 Version 1809: 10.0.17763.0 < 10.0.17763.3887, 10.0.0 < 10.0.17763.3887
- Windows Server 2019: 10.0.17763.0 < 10.0.17763.3887
- Windows Server 2019 (Server Core installation): 10.0.17763.0 < 10.0.17763.3887
- Windows Server 2022: 10.0.20348.0 < 10.0.20348.1487
- Windows 10 Version 20H2: 10.0.0 < 10.0.19042.2486
- Windows 11 version 21H2: 10.0.0 < 10.0.22000.1455
- Windows 10 Version 21H2: 10.0.19043.0 < 10.0.19044.2486
- Windows 11 version 22H2: 10.0.22621.0 < 10.0.22621.1105
- Windows 10 Version 22H2: 10.0.19045.0 < 10.0.19045.2486
- Windows 10 Version 1507: 10.0.10240.0 < 10.0.10240.19685
- Windows 10 Version 1607: 10.0.14393.0 < 10.0.14393.5648
- Windows Server 2016: 10.0.14393.0 < 10.0.14393.5648
- Windows Server 2016 (Server Core installation): 10.0.14393.0 < 10.0.14393.5648
- Windows 7: 6.1.0 < 6.1.7601.26321
- Windows 7 Service Pack 1: 6.1.0 < 6.1.7601.26321
- Windows 8.1: 6.3.0 < 6.3.9600.20778
- Windows Server 2008 Service Pack 2: 6.0.6003.0 < 6.0.6003.21872
- Windows Server 2008 Service Pack 2 (Server Core installation): 6.0.6003.0 < 6.0.6003.21872
- Windows Server 2008 Service Pack 2: 6.0.6003.0 < 6.0.6003.21872
- Windows Server 2008 R2 Service Pack 1: 6.1.7601.0 < 6.1.7601.26321
- Windows Server 2008 R2 Service Pack 1 (Server Core installation): 6.1.7601.0 < 6.1.7601.26321
- Windows Server 2012: 6.2.9200.0 < 6.2.9200.24075
- Windows Server 2012 (Server Core installation): 6.2.9200.0 < 6.2.9200.24075
- Windows Server 2012 R2: 6.3.9600.0 < 6.3.9600.20778
- Windows Server 2012 R2 (Server Core installation): 6.3.9600.0 < 6.3.9600.20778
- Fixed
- No fixed version is explicitly recorded in the structured CVE data.
- Action
- No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 10 Jan 2023 · Last source change 1 Jan 2025, 00:35 UTC · CWE-367 · Time-of-check Time-of-use (TOCTOU) Race Condition
CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2023-25722
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceOther authority
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.