Microsoft Patches Record 570 Windows Vulnerabilities in July Update, Including Three Actively Exploited Zero-Days
Microsoft has issued its largest monthly security update yet, releasing patches for a record 570 vulnerabilities across Windows and associated products. The July Patch Tuesday rollout includes three zero-day flaws, two of which were already being actively exploited in real attacks.
Fifty-nine of the issues received a critical severity rating. Of these, 48 allow remote code execution, nine enable privilege escalation, and the remainder involve security feature bypass or data tampering. The largest category of fixes addressed privilege escalation vulnerabilities, totaling 254, followed by 145 remote code execution flaws, 102 information disclosure issues, 35 denial-of-service problems, and 16 spoofing vulnerabilities.
The first actively exploited zero-day, CVE-2026-56155, affects Active Directory Federation Services. An authenticated attacker can abuse the flaw to obtain administrative privileges. Microsoft has not yet disclosed technical details of the observed attacks.
The second zero-day, CVE-2026-56164, resides in SharePoint Server. Due to missing authentication checks, a remote attacker can elevate privileges. As a temporary mitigation, Microsoft recommends enabling AMSI and full request-body scanning.
The third zero-day, CVE-2026-50661, was already publicly known before the update. It allows an attacker with physical access to bypass BitLocker encryption and access protected data. Microsoft had previously warned that the volume of patches would increase because the company is now using AI to hunt for vulnerabilities in the Windows source code.
The update touches numerous components, including multiple versions of .NET and .NET Framework, Active Directory Certificate Services, Active Directory Domain Services, Active Directory Federation Services, Azure Active Directory, Microsoft Office and Excel, Microsoft Defender, Exchange Server, and various Azure services. A selection of the addressed CVEs includes:
- .NET – CVE-2026-50649 (Remote Code Execution, Important), CVE-2026-50525 (Denial of Service, Important)
- Active Directory Federation Services – CVE-2026-56155 (Elevation of Privilege, Important)
- Microsoft Office – CVE-2026-55129, CVE-2026-55049, CVE-2026-55045 (Remote Code Execution, Critical)
- Microsoft Defender – CVE-2026-55012, CVE-2026-55011 (Remote Code Execution, Critical)
Security teams are strongly encouraged to deploy the updates as soon as possible to reduce exposure to both known and newly discovered threats.
Related articles
Security Week 2644: Active Exploitation of PHP2Shell Vulnerabilities Confirmed
PHP developers released patches for two critical vulnerabilities collectively known as PHP2Shell on October 20, affecting PHP 8.2 through 8.5 as well as older branches. The flaws allow unauthenticated remote code execution on affected servers, which power approximately 70 percent of websites. Despite expectations of immediate exploitation, confirmed attacks with working exploits only began on October 25. CrowdStrike noted technical difficulties in weaponizing the issues in real-world environments. Only one-fifth of top Russian websites had applied the fixes by October 25. Additional incidents included compromised eMudhra certificates, a critical GitLab flaw, and a 16-year-old Broadcom router vulnerability.
Positive Technologies Offers Up to 500,000 Rubles for Bypassing PT Application Firewall
Positive Technologies has expanded its Standoff Bug Bounty program to include rewards for bypassing its web application firewalls. Researchers can earn between 150,000 and 500,000 rubles for demonstrating practical bypasses against PT Application Firewall PRO and PT Application Firewall Cloud. The program targets the core protective mechanisms, including traffic filtering, attack detection rules, and the management layer used by administrators. Submissions must include reproducible attack scenarios that show how malicious requests can pass through undetected, rather than relying on scanner reports or theoretical findings. Reward amounts vary by severity and confirmed business impact, with critical issues in the PRO version paying up to 500,000 rubles. The company plans to use validated findings to strengthen detection rules and improve overall product resilience.
Tailscale SSH Vulnerability Allows Root Access via Unix Socket Redirection
A researcher identified flaws in Tailscale that let an attacker with existing SSH access on one node escalate to root privileges and move laterally across the network. Erica Windisch of Cyberdione Labs demonstrated the issues in lab conditions against Tailscale 1.104.2 and Headscale 0.29.5. The core problem stems from privileged operations performed by the tailscaled process when handling Unix socket redirection, granting an ordinary SSH session access to root-only resources. The researcher used the technique to interact with Docker and run elevated commands, and showed that broad access policies allow automated lateral movement in under a second. Additional issues include denial-of-service conditions and bypasses of certain restrictions. Recommendations include reviewing SSH policies and disabling unnecessary socket redirection, noting that Headscale 0.29.5 lacks an independent way to turn the feature off.
Critical CVE-2026-111497 Out-of-Bounds Write Flaw in Google Brotli Decoder Impacts Broad Range of Environments
A severe vulnerability has been identified in the Google-developed Brotli decoder used for decompressing data in web communications and other applications. The flaw, tracked as CVE-2026-111497, allows out-of-bounds writes when processing specially crafted compressed data, potentially enabling arbitrary code execution, information disclosure, or denial of service. It carries a CVSS v4.0 base score of 9.2 and is rated Critical. Google has released patched versions 1.2.1, 1.1.1, and 1.0.10 of the library. Node.js incorporated the fix in its updates, while Microsoft issued an out-of-band patch for .NET on October 25, 2026, to address the issue. The vulnerability affects any environment relying on the Brotli C implementation for data decompression.