HIGH
CVE-2026-40399
CWE-121Published: May 12, 2026· Updated: May 15, 2026
7.8
CVSS v3.1
EPSS:0.06%probability of exploitation in 30 daysPercentile:18.6th
Official Description
Stack-based buffer overflow in Windows TCP/IP allows an authorized attacker to elevate privileges locally.
Technical Analysis
CVE-2026-40399 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 7.8.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected Vendors & Products
Microsoft13 products
windows 10 1607windows 10 1809windows 10 21h2windows 10 22h2windows 11 23h2windows 11 24h2windows 11 25h2windows 11 26h1windows server 2016windows server 2019windows server 2022windows server 2022 23h2+1 more
Source: NVD CPE · 13 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (1)
Quick Facts
CVE IDCVE-2026-40399
CVSS Score7.8 / 10
SeverityHIGH
WeaknessCWE-121
CISA KEVNo
EPSS (30d)0.06%
Affected1 vendor
PublishedMay 12, 2026
Related CVEs (CWE-121)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-40399 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.