HIGH · CVSS 3.1 7.8CISA KEV · added 2025-02-11EPSS 1.57% (p75)Threat level 54
CVE-2025-21418: Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability
Microsoft · Windows · NVD published 2025-02-12 · posted 2025-02-11 · last modified 2026-06-17
What it is
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
| Weakness | CWE-122 |
|---|---|
| CVSS vector | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (source: [email protected]) |
| CISA due date | 2025-03-04 (for US federal agencies under BOD; a good deadline for everyone) |
| ATT&CK tactics | Privilege Escalation → Stealth → Collection |
Exploitation evidence
First exploit evidence seen: 2025-02-11 (earliest date across the sources below).
Exploited in the wild
- CISA KEV: listed since 2025-02-11. Source
Sources: CISA KEV.
Defend the Chain
The attack chain for CVE-2025-21418 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.
Threat level 54/100
Defender level 1 · 0 XP
Chain links broken: 0/3
Pick a red technique card on the board, then choose the defence that stops it.
Defend against T1068 Exploitation for Privilege Escalation CTID: exploitation technique
Exploiting this buffer overflow vulnerability could lead to an adversary gaining elevated privileges on the machine, leading to the potential for process injection using malicious code, as well as data loss.
How to fix it
CISA required action
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. (source: CISA KEV)
Fixed versions
- microsoft windows 10 1607: upgrade to 10.0.10240.20915 or later
- microsoft windows 10 1809: upgrade to 10.0.17763.6893 or later
- microsoft windows 10 21h2: upgrade to 10.0.19044.5487 or later
- microsoft windows 10 22h2: upgrade to 10.0.19045.5487 or later
- microsoft windows 11 22h2: upgrade to 10.0.22621.4890 or later
- microsoft windows 11 23h2: upgrade to 10.0.22631.4890 or later
- microsoft windows 11 24h2: upgrade to 10.0.26100.3107 or later
- microsoft windows server 2016: upgrade to 10.0.14393.7785 or later
- microsoft windows server 2019: upgrade to 10.0.17763.6893 or later
- microsoft windows server 2022: upgrade to 10.0.20348.3148 or later
- microsoft windows server 2022 23h2: upgrade to 10.0.25398.1425 or later
- microsoft windows server 2025: upgrade to 10.0.26100.3107 or later
Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.
Vendor advisories and patches
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21418 (CISA KEV notes)
MITRE ATT&CK mitigations for this chain
- M1051 Update Software (for T1068) : Update software regularly by employing patch management for internal enterprise endpoints and servers.
- M1050 Exploit Protection (for T1068) : Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploi
- M1048 Application Isolation and Sandboxing (for T1068) : Make it difficult for adversaries to advance their operation through exploitation of undiscovered or unpatched vulnerabilities by using sandboxing. Other types of virtualization and application microsegmentation may also mitigate the impact of some types of exploitation. Risks of additional exploits and weaknesses in t
- M1019 Threat Intelligence Program (for T1068) : Develop a robust cyber threat intelligence capability to determine what types and levels of threat may use software exploits and 0-days against a particular organization.
- M1038 Execution Prevention (for T1068) : Consider blocking the execution of known vulnerable drivers that adversaries may exploit to execute code in kernel mode. Validate driver block rules in audit mode to ensure stability prior to production deployment.
- M1026 Privileged Account Management (for T1055) : Utilize Yama (ex: /proc/sys/kernel/yama/ptrace_scope) to mitigate ptrace based process injection by restricting the use of ptrace to privileged users only. Other mitigation controls involve the deployment of security kernel modules that provide advanced access control and process restrictions such as SELinux, grsecurit
- M1040 Behavior Prevention on Endpoint (for T1055) : Some endpoint security solutions can be configured to block some types of process injection based on common sequences of behavior that occur during the injection process. For example, on Windows 10, Attack Surface Reduction (ASR) rules may prevent Office applications from code injection.
- M1057 Data Loss Prevention (for T1005) : Data loss prevention can restrict access to sensitive data and detect sensitive data that is unencrypted.
Detection Generic guidance
- Privilege Escalation: Alert on processes gaining SYSTEM/root unexpectedly, and on exploitation crashes of privileged services.
- Collection: Watch for bulk reads of databases, file shares or mailboxes by the affected service.
Response checklist Generic guidance
- Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
- Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
- Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
- Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.