CVE-2026-105005 in Windows
Summary
by MITRE • 10/13/2026
Out-of-bounds write in Windows Schannel allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves a critical out-of-bounds write flaw within the Secure Channel (Schannel) security support provider on Microsoft Windows operating systems. Schannel is responsible for implementing SSL, TLS, and other cryptographic protocols that secure communications between clients and servers. This specific memory corruption issue arises when the component processes specially crafted network packets or malformed data structures during the negotiation of a secure connection. An unauthorized attacker can exploit this flaw by sending maliciously constructed traffic to a vulnerable system, triggering an invalid write operation beyond the boundaries of allocated memory buffers.
From a technical perspective, out-of-bounds writes are among the most dangerous classes of software vulnerabilities because they allow attackers to overwrite adjacent memory locations with arbitrary data. In the context of Schannel, this corruption can affect critical control structures such as function pointers or exception handlers within the process space. By carefully crafting the payload, an attacker can manipulate these overwritten values to redirect execution flow. This mechanism enables remote code execution without requiring any user interaction or authentication credentials, making it a high-severity threat vector that allows full system compromise over the network.
The operational impact of this vulnerability is severe due to its potential for widespread exploitation across enterprise environments relying on encrypted communications. Since Schannel underpins many common protocols including HTTPS, SMTPS, and IMAPS, any service utilizing these standards could be at risk if it accepts connections from untrusted sources or processes external input without sufficient validation. Successful exploitation grants the attacker the same privileges as the application running Schannel, which often includes SYSTEM-level access depending on the configuration. This level of access allows for complete control over the affected machine, facilitating data exfiltration, lateral movement within a network, and persistence through backdoor installation or credential theft.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-787: Out-of-bounds Write, which describes writing to a memory location outside of the intended buffer boundaries. In terms of offensive security frameworks, this exploit technique corresponds to MITRE ATT&CK tactic T1203: Exploitation for Client Execution and specifically techniques involving remote code execution via network protocols such as T1571 or general exploitation patterns like T1190. The lack of authentication requirement places it in the initial access phase where adversaries leverage software vulnerabilities to gain a foothold before escalating privileges or moving laterally.
Mitigation strategies must prioritize immediate patching through official Microsoft security updates that address this specific memory corruption issue within Schannel. Organizations should verify that all Windows endpoints are updated with the latest cumulative patches and hotfixes released by Microsoft for their respective operating system versions. In environments where patching is not immediately feasible, network segmentation can help limit exposure by restricting access to vulnerable services from untrusted networks. Additionally, deploying intrusion detection systems configured to detect anomalous TLS handshake patterns or malformed packet structures may provide an additional layer of defense against exploitation attempts while permanent fixes are applied.