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Microsoft Patch Tuesday, September 2026 Security Update Review
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, including 113 critical and two actively exploited Windows privilege escalation flaws.
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, its largest release ever, including 113 critical and 860 important, covering Windows HTTP.sys, Hyper-V, Entra ID, Exchange Server, Office, DNS, and more. Two zero-days are confirmed exploited in the wild: CVE-2026-81963 (Windows Update Stack EoP) and CVE-2026-85880 (ALPC heap overflow), both letting authenticated attackers gain SYSTEM privileges. Notable criticals include an Entra ID authentication bypass (CVE-2026-62916) and multiple Windows DNS Server and Office remote code execution flaws.
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VU#431093: TCG TPM 2.0 reference code found vulnerable to information leakage and timing side-channel attacks
CERT/CC discloses two TPM 2.0 reference code flaws allowing RSA key decryption and forged TPM attestations via crafted commands.
CERT/CC published VU#431093 covering two vulnerabilities in the TCG TPM 2.0 reference implementation: CVE-2026-6726 (information leakage via falsified TPM keys) and CVE-2026-6727 (timing side-channel in RSA OAEP decryption). An attacker with privileged access to a TPM command interface could send crafted TPM commands to decrypt ciphertexts for affected TPM-managed RSA keys, including the RSA Endorsement Key, or obtain credentials enabling forged TPM 2.0 attestations. Remediation is tracked in TCGVRT010 and TCGVRT0011.
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Microsoft’s September 2026 Patch Tuesday addresses 964 CVEs (CVE-2026-81963, CVE-2026-85880)
Microsoft's September 2026 Patch Tuesday fixes a record 964 CVEs, including two zero-days actively exploited in the wild.
Microsoft patched a record 964 CVEs in its September 2026 Patch Tuesday release, with 101 rated critical and 824 rated important, making it the largest Patch Tuesday to date. The release includes fixes for two zero-days that were exploited in the wild, with CVE-2026-81963 and CVE-2026-85880 highlighted in the release. Affected products span Windows core components, Office, Exchange, .NET, Visual Studio, Active Directory services (including AD CS and AD FS) and numerous Azure services. Tenable notes the release surpasses July's as the biggest ever.
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New Passkey Attacks Can Recover Synced Private Keys or Bypass Phishing
Three research teams showed passkey bypasses: WebAuthn assertion replay in Microsoft Entra ID, synced-passkey key recovery in Google Password Manager, and Windows Hello key reuse.
SpecterOps' Pass-the-Passkey research showed Windows stored past YubiKey signatures in cleartext and chained this with Microsoft Entra ID passkey validation weaknesses to impersonate privileged users despite phishing-resistant MFA; the Windows Event Logging Service issue is tracked as CVE-2026-34348 (CVSS 6.5) and fixed in July 2026 updates. Unit 42's Golden Pass-ta-key attack recovered the 32-byte Security Domain Secret protecting Google Password Manager synced passkeys from Chrome on Windows via pre-existing malware. Dirk-jan Mollema showed in-session malware can use a hardware-bound Windows Hello for Business key without a fresh PIN or biometric check. Microsoft applied Entra-side mitigations for the relay assertion issue; no real-world exploitation has been reported.
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Microsoft Patch Tuesday updates for January 2025 fixed three actively exploited flaws
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Microsoft patches 12 critical vulnerabilities, nine of which are in Layer 2 Tunneling Protocol
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Microsoft Rolls Out Patches for 80 New Security Flaws — Two Under Active Attack
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New Dell BIOS Bugs Affect Millions of Inspiron, Vostro, XPS, Alienware Systems
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