Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability
Microsoft · Windows
The flaw is a heap-based buffer overflow in the Windows Ancillary Function Driver for WinSock (afd.sys), a component of Microsoft Windows that handles socket-related operations. The vulnerability is an elevation of privilege issue within that driver. An attacker with local access and low-privileged credentials, requiring no user interaction, could exploit the overflow to gain elevated privileges on the affected system.
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 3/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited the day it was disclosed.
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
3 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order 3Privilege EscalationTA0004
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.
CollectionTA0009
Detection
0 rules for this CVE · 82 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2025-21418 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Exploitation for Privilege EscalationT106831 general rules
- Exploiting CVE-2019-1388criticalstable
- Audit CVE Eventcriticaltest
- HackTool - SysmonEOP Executioncriticaltest
- InstallerFileTakeOver LPE CVE-2021-41379 File Create Eventcriticaltest
- Possible Coin Miner CPU Priority Paramcriticaltest
- Potential CVE-2021-41379 Exploitation Attemptcriticaltest
- Potential SystemNightmare Exploitation Attemptcriticaltest
- Sudo Privilege Escalation CVE-2019-14287 - Builtincriticaltest
Process InjectionT105537 general rules
- Antivirus PrinterNightmare CVE-2021-34527 Exploit Detectioncriticalstable
- Potential Dridex Activitycriticalstable
- CobaltStrike Named Pipecriticaltest
- CobaltStrike Named Pipe Pattern Regexcriticaltest
- HackTool - DInjector PowerShell Cradle Executioncriticaltest
- Malicious Named Pipe Createdcriticaltest
- RedSun - Named Pipe Createdcriticalexperimental
- RedSun - TieringEngineService.exe Detected as EICAR Test Filecriticalexperimental
Data from Local SystemT100514 general rules
- OpenCanary - SMB File Open Requesthightest
- Potential Conti Ransomware Database Dumping Activity Via SQLCmdhightest
- SQLite Chromium Profile Data DB Accesshightest
- SQLite Firefox Profile Data DB Accesshightest
- VeeamBackup Database Credentials Dump Via Sqlcmd.EXEhightest
- Script Interpreter Spawning Credential Scanner - Linuxhighexperimental
- Script Interpreter Spawning Credential Scanner - Windowshighexperimental
- Shai-Hulud NPM Package Malicious Exfiltration via Curlhighexperimental
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 30, 202629 Oct 2026
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- 44 more on OTX