Microsoft breaks Patch Tuesday record with 974-CVE deluge

CVE-2026-55007 is a double-free memory corruption flaw (CWE-415) in Microsoft Exchange Server in which the same heap allocation is freed twice, corrupting memory. A remote, unauthenticated attacker can trigger the flaw over the network, though the high attack complexity (AC:H) means reliable exploitation likely depends on favorable heap/timing conditions, making it harder to weaponize than typical pre-auth RCEs. Successful exploitation yields arbitrary code execution with high impact on confidentiality, integrity, and availability (CVSS 3.1: 8.1). Any organization running on-premises Microsoft Exchange Server is in scope, with the greatest risk on servers reachable from untrusted networks. As of now there is no public proof-of-concept, the flaw is not in CISA's KEV catalog, and EPSS estimates only a 0.7% chance of exploitation within 30 days; it was disclosed amid Microsoft's record September 2026 Patch Tuesday (974 CVEs), which press coverage highlighted for notable Exchange flaws.

Do: Apply Microsoft's September 2026 Exchange Server security updates as soon as possible, prioritizing internet-facing servers (OWA/ECP and SMTP endpoints); since affected version ranges are not included in this data, confirm affected versions and fixed builds in Microsoft's advisory for CVE-2026-55007. Until patched, restrict untrusted network access to Exchange endpoints, and monitor the MSRC advisory and KEV for exploitation updates given the high-severity, pre-authentication nature of the flaw.

Adobe Commerce and Magento (including Adobe Commerce B2B) contain an improper neutralization of special elements used in a template engine (CWE-1336), a template-injection flaw that permits arbitrary code execution in the context of the current user. The flaw is reachable over the network by unauthenticated attackers, requires no user interaction, and its changed scope (CVSS 3.1 S:C) means injected code executes beyond the vulnerable component, producing a maximum-severity (CVSS 10.0) remote code execution condition. A successful attacker gains arbitrary code execution on the storefront server; in the observed campaign, intruders installed a Rust backdoor and a PHP web shell (dubbed 'StyleSmuggler') on compromised servers. Any organization running an Adobe Commerce, Adobe Commerce B2B, or Magento storefront is in scope, with internet-facing e-commerce deployments most exposed. Exploitation is confirmed in the wild: the bug was abused as a zero-day before patching and was added to CISA's Known Exploited Vulnerabilities catalog on 2026-09-08.

Do: Apply Adobe's released patches immediately per vendor instructions, prioritizing internet-facing Commerce/Magento storefronts, and ensure compliance with CISA BOD 26-04 timelines for KEV entries. Hunt for 'StyleSmuggler' indicators of compromise, including unexpected Rust backdoor binaries and PHP web shells on hosts, and review template/theme customizations for tampering. Exact fixed version numbers are not included in the available data, so consult Adobe's advisory for the correct patched release for your Commerce/Magento version line.

CVE-2026-81963 is a link-following flaw (CWE-59, improper link resolution before file access) in the Microsoft Windows Update Stack, in which the component fails to correctly resolve file links before opening them. A local attacker with low privileges can plant or manipulate a link (symlink/junction) that the privileged update stack follows during operation, redirecting its file access to an attacker-controlled target. The result is local privilege escalation — CVSS 3.1 rates this 7.8 (high) with high confidentiality, integrity, and availability impact — allowing an authorized local user or malware already on the machine to gain elevated rights. Affected products are Windows 11 23H2, 24H2, 25H2, and 26H1 and Windows Server 2025; any unpatched system on those versions is exposed to any local account holder. The flaw was fixed in Microsoft's record September 2026 Patch Tuesday (974 CVEs), was added to CISA's KEV on 2026-09-08 as one of two Windows zero-days reported as exploited in the wild, and has no known public PoC or confirmed ransomware use.

Do: Immediately deploy the September 2026 Patch Tuesday cumulative updates to every Windows 11 23H2/24H2/25H2/26H1 and Windows Server 2025 host; as a KEV entry under BOD 26-04, prioritize internet-exposed and high-value assets, apply vendor mitigations (or discontinue use) where patching is delayed, and follow CISA's forensics triage requirements if compromise is suspected. Verify deployment via patch telemetry and review which local accounts can trigger update-stack activity on shared or multi-user systems.

CVE-2026-85045 is a race condition (CWE-367, a time-of-check-to-time-of-use flaw) in the V8 JavaScript engine used by Google Chrome. An attacker triggers it by persuading a user to open a specially crafted HTML page, in which a timing window during V8's handling of an object leaves stale state that the attacker can leverage. Successful exploitation lets a remote attacker execute arbitrary code inside Chrome's renderer sandbox (but not escape it), yielding code execution at the browser's sandboxed privilege level; CVSS 3.1 rates this 7.5 High with a network vector, high attack complexity, and required user interaction. All Google Chrome installations running versions prior to 152.0.7977.82 are affected, which given Chrome's ubiquity means effectively every unpatched desktop and mobile Chrome deployment worldwide. No public proof-of-concept is known, the flaw is not on the CISA KEV catalog, and EPSS estimates a ~0.2% chance of exploitation within 30 days, though related reporting describes a sibling Chrome zero-day (CVE-2026-85046) exploited in the wild, signaling active attacker interest in this V8 code.

Do: Update Google Chrome to 152.0.7977.82 or later on all endpoints and enforce the minimum version centrally (MDM/GPO/Intune/EDR), prioritizing internet-facing and high-risk users. Because the related Chrome zero-day CVE-2026-85046 was reportedly exploited in the wild and was addressed in the same release, treat this patch cycle as urgent. Also verify browser versions in any Chromium-based derivatives in your fleet, which typically pick up the V8 fix on their own release schedules.

Google Chrome versions prior to 152.0.7977.82 contain a type confusion flaw (CWE-843) in the V8 JavaScript engine, which mishandles object types during engine operations (public proof-of-concept writeups indicate it is reachable through array sorting and WebAssembly-related code paths). A remote attacker triggers the flaw simply by getting a user to open a crafted HTML page, with no privileges or authentication required. Successful exploitation lets the attacker execute arbitrary code inside the browser's sandbox, and public reporting shows it being chained with Windows zero-days (the 'BlueMoon' exploit kit) by Chinese espionage groups for broader compromise. Any user of an unpatched Chrome or another build embedding the affected V8 engine is exposed. The vulnerability is a zero-day that was actively exploited in the wild before patching, was added to CISA's KEV on 2026-09-04, and has five public proof-of-concept references.

Do: Update Google Chrome to 152.0.7977.82 or later immediately, and apply the corresponding V8 fix in any Chromium-based browser in use. Federal agencies must apply mitigations in line with CISA BOD 26-04 and its cloud-services requirements, evaluating each asset's internet exposure. Because public reporting shows this flaw chained with Windows zero-days in 'BlueMoon' attacks, patch the related Windows vulnerabilities as well and hunt for signs of exploit-chain activity on high-exposure endpoints.