A newly analyzed local privilege escalation vulnerability in the Windows Error Reporting (WER) service<\/a> allows attackers to easily gain full SYSTEM access.<\/p>\n The flaw, tracked as CVE-2026-20817<\/a>, was considered so structurally dangerous that Microsoft completely removed the vulnerable feature rather than attempting a traditional code patch.\u200b<\/p>\n The security flaw exists within the main executable library of the Windows Error Reporting service, specifically the\u00a0 According to vulnerability researchers Denis Faiustov and Ruslan Sayfiev at GMO Cybersecurity, the service suffers from improper handling of insufficient permissions<\/a> when processing specific client requests.<\/p>\n This architectural weakness provides a reliable pathway for a low-privileged local user to trigger an elevated command execution primitive.<\/p>\n Historically, the Windows Error Reporting service has been a frequent target for privilege escalation attacks<\/a> due to its complex inter-process communication requirements.<\/p>\n To exploit this specific flaw, the attacker must first connect to the ALPC port using the\u00a0 The malicious data structure must contain exactly the right\u00a0 The core of this vulnerability involves the manipulation of Advanced Local Procedure Call (ALPC)<\/a> messages sent to the\u00a0 An attacker crafts a message containing a File Mapping object<\/a>, prompting the internal Ultimately, the\u00a0 Security analysts performing binary diffing<\/a> between versions 10.0.26100.7309 and 10.0.26100.7623 of the\u00a0 Instead of adding permission checks or input sanitization routines, developers introduced a If the patched code is executed, the function immediately returns an While the vulnerability successfully forces the execution of\u00a0 During the exploit process, the WER service uses parent process ID spoofing to make the new elevated process appear as a direct child of the attacker\u2019s low-privileged client.<\/p>\n Because this specific process spoofing technique is heavily abused by modern malware, security solutions like Microsoft Defender<\/a> actively detect the behavior and raise immediate alerts.<\/p>\n Cybersecurity professionals must remain highly vigilant when researching this specific local privilege escalation threat.<\/p>\n Multiple fake and potentially malicious proof-of-concept repositories for CVE-2026-20817 have appeared on platforms like GitHub.<\/p>\n These deceptive project files often contain hidden malware payloads<\/a>, serving as a critical reminder to carefully isolate and statically analyze all downloaded security tools before execution.<\/p>\n Follow us on Google News<\/a>, LinkedIn<\/a>, and X<\/a> for daily cybersecurity updates. Contact us<\/a> to feature your stories.<\/strong><\/p>\n The post New Windows Error Reporting Vulnerability Lets Attackers Escalate to Gain SYSTEM Access<\/a> appeared first on Cyber Security News<\/a>.<\/p>\n<\/div>\nWerSvc.dll<\/code>\u00a0file.<\/p>\nNtAlpcConnectPort\u00a0API <\/code>and subsequently send their payload using the\u00a0NtAlpcSendWaitReceivePort\u00a0API<\/code>.<\/p>\nMessageFlags<\/code>\u00a0parameter and structural padding to successfully trigger the vulnerable dispatcher logic.<\/p>\nThe Exploitation Mechanism<\/strong><\/h2>\n
WindowsErrorReportingServicePort<\/code>\u00a0endpoint.<\/p>\n![\"Proof-of-Concept(source](\"https:\/\/i0.wp.com\/blogger.googleusercontent.com\/img\/b\/R29vZ2xl\/AVvXsEjDxSMFcqoa9mRESCV1se_qJ_jSo_ANeF3aPxdlzDlUWnF5RWZxsjgC_kRlsySb8vv_hI2kYmLFTAtblk2D1CYJ4VNefxuBGilXTLR7wd9gDU1BCUJs9eCTTqM1cRseEM4MG_d7dCqnv4JjLS7o-GnBVBMyxbVWThVMqNVvfRhsgm5WG_x1jN0Vl1ohze0\/s1600\/Screenshot%25202026-03-27%2520114751%2520%25281%2529.webp?ssl=1\")
\u00a0ElevatedProcessStart<\/code>\u00a0function to duplicate the handle and read the malicious command-line arguments using the\u00a0MapViewOfFile<\/code>\u00a0API.<\/p>\nCreateElevatedProcessAsUser<\/code>\u00a0function is called, which inadvertently launches the legitimate\u00a0WerFault.exe<\/code>\u00a0application with highly privileged SYSTEM rights and the attacker\u2019s heavily controlled parameters.<\/p>\nWerSvc.dll<\/code>\u00a0file discovered that Microsoft took an unusually aggressive approach to remediation.<\/p>\nstrict\u00a0__private_IsEnabled()<\/code>\u00a0feature test that permanently disables the\u00a0SvcElevatedLaunch<\/code>\u00a0functionality.<\/p>\n\u00a00x80004005\u00a0(E_FAIL)<\/code> error code, effectively neutralizing the entire attack surface by removing the feature entirely.\u200b<\/p>\nWeaponization and Detection<\/strong><\/h2>\n
WerFault.exe<\/code>\u00a0as SYSTEM, attackers must combine specific command-line options with advanced Windows internal tricks to achieve arbitrary code execution.<\/p>\n![\"Suspicious](\"https:\/\/i0.wp.com\/blogger.googleusercontent.com\/img\/b\/R29vZ2xl\/AVvXsEgQJ3UozgxsgUV7qG5IuKYaavd_IKM8tVCakD_D8Ksta_Fm_ogUs6UejkOUKuzDgudLlqGxHvZQlfi6fK1b8FcwdIjL_VLv1UCW9DMnDaTvhzhhqKzAyaKw1r0514rnVVrz1qdYtdz0YcZZiKk84p4UOxzKDOYS1bjpU8mSZwBlyE5QQDCwM-MZicv_li4\/s1600\/Screenshot%25202026-03-27%2520114810%2520%25281%2529.webp?ssl=1\")