# CVE-2026-55040 — Microsoft SharePoint Enterprise Server 2016 > As of 2026-07-14, CVE-2026-55040 is a CRITICAL-severity vulnerability in Microsoft SharePoint Enterprise Server 2016, CVSS v3.1 9.1. Threadlinqs Intelligence links 13 tracked threat campaigns to CVE-2026-55040, most recently “Microsoft August 2026 Patch Tuesday: 400 Flaws Fixed, Including Lazarus-Exploited Zero-Day CVE-2026-68820 (AFD.sys) and Two Publicly Disclosed Zero-Days (CVE-2026-62832 "LegacyHive", CVE-2026-72971)”. **Last updated:** 2026-07-14 ## What is CVE-2026-55040? Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network. The record classifies CVE-2026-55040 under weakness class [CWE-1390](https://cwe.mitre.org/data/definitions/1390.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 3 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 60 days ago. ## Severity and exploitation probability - **CVSS v3.1 base score:** 9.1 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C`) - **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog - **Threadlinqs priority:** 4.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability - **Published:** 2026-07-14 ## Is CVE-2026-55040 being exploited? No public exploitation evidence for CVE-2026-55040 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-07-14. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited. ## Affected products and versions - **Microsoft**: SharePoint Enterprise Server 2016, SharePoint Server 2019, SharePoint Server Subscription Edition ## How to fix CVE-2026-55040 No vendor patch reference has been recorded for CVE-2026-55040 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise. ## Threat activity tracking CVE-2026-55040 13 tracked threats in the Threadlinqs corpus reference CVE-2026-55040, either in the campaign’s CVE list or as an indicator on the campaign record. - [Microsoft August 2026 Patch Tuesday: 400 Flaws Fixed, Including Lazarus-Exploited Zero-Day CVE-2026-68820 (AFD.sys) and Two Publicly Disclosed Zero-Days (CVE-2026-62832 "LegacyHive", CVE-2026-72971)](https://intel.threadlinqs.com/threat/TL-2026-1987) — CRITICAL · 2026-08-11 - [CISA Adds Exploited SharePoint RCE Zero-Day CVE-2026-58644 to KEV Catalog](https://intel.threadlinqs.com/threat/TL-2026-1434) — CRITICAL · 2026-07-17 - [July 2026 Patch Tuesday: Actively Exploited SharePoint RCE (CVE-2026-58644) and AD FS/SharePoint Zero-Days](https://intel.threadlinqs.com/threat/TL-2026-1437) — CRITICAL · 2026-07-17 - [CVE-2026-58644: Microsoft SharePoint Server Unauthenticated Remote Code Execution Exploited in the Wild](https://intel.threadlinqs.com/threat/TL-2026-1460) — CRITICAL · 2026-07-17 - [Microsoft July 2026 Patch Tuesday: Two Actively Exploited Zero-Days in AD FS (CVE-2026-56155) and SharePoint (CVE-2026-56164), Plus Unpatched BitLocker Bypass (CVE-2026-50661)](https://intel.threadlinqs.com/threat/TL-2026-1350) — CRITICAL · 2026-07-15 - [Actively Exploited SharePoint Server Elevation of Privilege Flaw (CVE-2026-56164) Patched Alongside Critical RCE Pair in July 2026 Patch Tuesday](https://intel.threadlinqs.com/threat/TL-2026-1364) — CRITICAL · 2026-07-15 - [CVE-2026-56164: Microsoft SharePoint Server Missing-Authentication Vulnerability Actively Exploited, Added to CISA KEV](https://intel.threadlinqs.com/threat/TL-2026-1369) — CRITICAL · 2026-07-15 - [July 2026 Patch Tuesday: Microsoft Fixes 622 CVEs Including Three Actively-Targeted Zero-Days (CVE-2026-56155 AD FS EoP, CVE-2026-56164 SharePoint EoP, CVE-2026-50661 BitLocker Bypass)](https://intel.threadlinqs.com/threat/TL-2026-1372) — CRITICAL · 2026-07-15 - [CISA Warns of Trio of Actively Exploited SharePoint Server Flaws (CVE-2026-32201, CVE-2026-45659, CVE-2026-56164)](https://intel.threadlinqs.com/threat/TL-2026-1378) — CRITICAL · 2026-07-15 - [Microsoft July 2026 Patch Tuesday: 570 Flaws Fixed, 3 Zero-Days Including AD FS and SharePoint Privilege Escalation](https://intel.threadlinqs.com/threat/TL-2026-1324) — CRITICAL · 2026-07-14 - [Microsoft July 2026 Patch Tuesday: Record 622 Flaws Fixed, Two Zero-Days Under Active Exploitation (CVE-2026-56164, CVE-2026-56155)](https://intel.threadlinqs.com/threat/TL-2026-1334) — CRITICAL · 2026-07-14 - [July 2026 Patch Tuesday: Two Actively Exploited Microsoft Zero-Days (SharePoint EoP CVE-2026-56164, AD FS EoP CVE-2026-56155) Plus SharePoint JWT Auth Bypass CVE-2026-55040](https://intel.threadlinqs.com/threat/TL-2026-1339) — HIGH · 2026-07-14 - [CVE-2026-55040: Microsoft SharePoint JWT Token Authentication Bypass (Unpatched Chain Component, PoC Public)](https://intel.threadlinqs.com/threat/TL-2026-1341) — CRITICAL · 2026-07-14 ## Sources Enriched from CVE.org, NVD, GitHub Security Advisories. Last verified by Threadlinqs on 2026-07-15. This product uses the NVD API but is not endorsed or certified by the NVD. **Vendor advisory and patch** - [msrc.microsoft.com — vendor advisory](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040) Canonical: https://intel.threadlinqs.com/cve/CVE-2026-55040 Full detection coverage and IOCs for threats exploiting CVE-2026-55040 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp