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. 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) — CRITICAL · 2026-08-11
- CISA Adds Exploited SharePoint RCE Zero-Day CVE-2026-58644 to KEV Catalog — CRITICAL · 2026-07-17
- July 2026 Patch Tuesday: Actively Exploited SharePoint RCE (CVE-2026-58644) and AD FS/SharePoint Zero-Days — CRITICAL · 2026-07-17
- CVE-2026-58644: Microsoft SharePoint Server Unauthenticated Remote Code Execution Exploited in the Wild — 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) — 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 — CRITICAL · 2026-07-15
- CVE-2026-56164: Microsoft SharePoint Server Missing-Authentication Vulnerability Actively Exploited, Added to CISA KEV — 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) — CRITICAL · 2026-07-15
- CISA Warns of Trio of Actively Exploited SharePoint Server Flaws (CVE-2026-32201, CVE-2026-45659, CVE-2026-56164) — CRITICAL · 2026-07-15
- Microsoft July 2026 Patch Tuesday: 570 Flaws Fixed, 3 Zero-Days Including AD FS and SharePoint Privilege Escalation — 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) — 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 — HIGH · 2026-07-14
- CVE-2026-55040: Microsoft SharePoint JWT Token Authentication Bypass (Unpatched Chain Component, PoC Public) — CRITICAL · 2026-07-14
Sources
Enriched from CVE.org, NVD, GitHub Security Advisories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.
Vendor advisory and patch
← all vulnerabilities · Markdown version · Threadlinqs Intelligence