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September 2026 Patch Tuesday: Record patch count, 2 zero-days, and a SigRed successor
Microsoft's September 2026 Patch Tuesday delivers a record patch count, fixing two exploited zero-days and a wormable DNS flaw dubbed a SigRed successor.
Microsoft's September 2026 Patch Tuesday sets another record patch count, fixing two vulnerabilities exploited as zero-days: CVE-2026-81963, a Windows Update Stack low-privilege-to-SYSTEM escalation reported by MSTIC, and CVE-2026-85880, a Windows Advanced Local Procedure Call escalation reported by Proofpoint. Zero Day Initiative's Dustin Childs urges priority on a cluster of 20 potentially wormable bugs including DNS RCE CVE-2026-69730, described as a spiritual successor to SigRed, plus Kerberos authentication bypass CVE-2026-69676 that could give any authenticated domain user RCE on domain controllers, and Exchange RCE CVE-2026-55007 via a malicious Visio attachment. All Windows fixes are bundled in cumulative updates, and experts stress prioritizing exploitable, reachable flaws over raw patch counts.
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AL26-019 - Vulnerabilities impacting Citrix NetScaler ADC and NetScaler Gateway - CVE-2026-19490 and CVE-2026-19489
Canadian Cyber Centre alerts on Citrix NetScaler ADC/Gateway flaws CVE-2026-19490 (authentication bypass) and CVE-2026-19489 (buffer overflow), urging emergency patching.
The Canadian Centre for Cyber Security issued alert AL26-019 covering two Citrix NetScaler vulnerabilities disclosed in a vendor advisory on August 19, 2026. CVE-2026-19490 (CWE-288) allows a remote unauthenticated attacker to bypass authentication on appliances configured as a Gateway for SSL VPN, ICA Proxy, CVPN, RDP Proxy, or as an AAA virtual server. CVE-2026-19489 (CWE-120) is a classic buffer overflow that may cause memory overflow, unpredictable behavior, or denial-of-service conditions. Affected appliances are vulnerable when configured as a SAML IdP; fixed versions include 14.1-73.32, 13.1-63.21, and 13.1-37.277 for FIPS.
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CISA Red Team Fully Compromised Two Critical Infrastructure Orgs
CISA red teams achieved full domain and cloud compromise at two critical infrastructure orgs; one SOC never detected the intrusion.
CISA advisory AA26-237A documents two simultaneous red team assessments. Organization A (Government Services sector) missed the intrusion entirely, as default credentials on a web app, ADCS ESC1 abuse, and thousands of false-positive alerts let the red team reach sensitive business systems and read SOC email. Organization B (Water/Wastewater sector) detected, isolated, and reimaged hosts quickly, but both orgs lacked Conditional Access for workload identities, and B still exposed DCSync, Golden Ticket, and OT network attack paths.
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