What is CVE-2026-45659?
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
The record classifies CVE-2026-45659 under weakness class CWE-502. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 3 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 159 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.8 — HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 2.7% probability of exploitation in the next 30 days, higher than 85.5% of all scored CVEs
- CISA KEV
- Listed since 2026-07-01, federal remediation deadline 2026-07-04 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2026-05-22, last modified 2026-08-11
Is CVE-2026-45659 being exploited?
CISA added CVE-2026-45659 to the Known Exploited Vulnerabilities catalog on 2026-07-01, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-07-04 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2026-45659 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 44 in the Threadlinqs vulnerability feed.
- HORKimhab/CVE-2026-45659 (github)
Affected products and versions
- Microsoft: SharePoint Enterprise Server 2016, SharePoint Server 2019, SharePoint Server Subscription Edition
How to fix CVE-2026-45659
Because CVE-2026-45659 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-07-04. No vendor patch reference has been recorded for CVE-2026-45659 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-2026-45659
17 tracked threats in the Threadlinqs corpus reference CVE-2026-45659, either in the campaign’s CVE list or as an indicator on the campaign record.
- 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
- CISA Warns of Active Exploitation of Three Microsoft SharePoint Server Vulnerabilities (CVE-2026-32201, CVE-2026-45659, CVE-2026-56164) — 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: 569 CVEs, Two Actively Exploited Zero-Days (CVE-2026-56155 AD FS EoP, CVE-2026-56164 SharePoint EoP) — 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
- CVE-2026-45659: SharePoint Deserialization RCE Added to CISA KEV Amid Storm-2603 Exploitation — HIGH · 2026-07-02
- CVE-2026-45659: Microsoft SharePoint Server Deserialization RCE Added to CISA KEV — HIGH · 2026-07-02
- CVE-2026-45659: Microsoft SharePoint Server Deserialization RCE Actively Exploited, Added to CISA KEV — CRITICAL · 2026-07-02
- CVE-2026-45659: Microsoft SharePoint Deserialization RCE Actively Exploited, Added to CISA KEV — HIGH · 2026-07-02
- CVE-2026-45659: Microsoft SharePoint Deserialization RCE Added to CISA KEV Despite 'Exploitation Less Likely' Rating — HIGH · 2026-07-02
- CISA KEV Addition: Microsoft SharePoint Server Deserialization RCE (CVE-2026-45659) Actively Exploited by Storm-2603 / Warlock Ransomware — CRITICAL · 2026-07-01
- Microsoft SharePoint Authenticated RCE via Deserialization of Untrusted Data (CVE-2026-45659) — HIGH · 2026-05-26
Sources
Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on .