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CVE-2026-58644

Exploitation: active CVSS 9.8 CRITICAL

CVSS base score: 9.8 (Critical) vendor CNA · v3.1

Score assigned by the vendor's own CVE Numbering Authority (CNA); CISA's Vulnrichment program adds a score only when the CNA omits one.

Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

Vendor: Microsoft   Product: SharePoint

Description

Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.

Lifecycle Timeline

Each milestone comes from a different source, so gaps between them are gaps in what those sources publish, not evidence that nothing happened. EPSS history for this CVE holds 22 points from 2026-07-18, tracked daily from 2026-09-09; earlier points are weekly, which dates a spike to within a week. Peak probability 60.9% on 2026-09-21.

Published Applicability

CVE List v5 (CNA container) 6 affected · 0 fixed · 0 not affected

Check whether a specific version is affected →

What each source publishes about which product versions carry this vulnerability, kept as written rather than merged. Absence here means no source has published applicability data, not that nothing is affected.

Research & News Coverage

DateSourceArticle
2026-07-17 The Hacker News CISA Adds Exploited SharePoint RCE Zero-Day CVE-2026-58644 to KEV

Articles from monitored vendor research blogs and security news feeds that specifically mention this CVE. Coverage begins when feed monitoring started; earlier articles are not indexed.

Detection & Exploitation

Scan
Exploit / Pen Test
none published
Host / SIEM
none published

Coverage across public collections only: Nuclei and OpenVAS NVT (scan); Snort and Suricata ET Open (network); Sigma and YARA (host/SIEM); Metasploit, Exploit-DB and public GitHub repositories (exploit). Absence here means nothing public was found, not that detection is impossible.
GitHub PoC repositories are collected automatically by PoC-in-GitHub (CC0) and are not vetted: some are fakes and some are malware. Treat them as evidence that code was published, not as code to run.
OpenVAS coverage derives from the Greenbone Community Feed, made available under the Open Database License (ODbL) v1.0; its individual Vulnerability Tests are licensed GNU GPL v2.

Microsoft Assessment

published by the affected vendor via MSRC

Microsoft SharePoint Remote Code Execution Vulnerability

Exploitation Detected
Yes
No
Critical
Remote Code Execution
Microsoft Office SharePoint
2026-07-14

The vendor's own judgement about their own code, shown alongside CISA's rather than merged into it. The exploitability index is a forward-looking prediction, distinct from a CVSS severity or CISA's SSVC decision, and vendors often report observed exploitation before a CVE reaches the KEV catalog. Vendor advisory →

CISA Assessment (Vulnrichment / SSVC)

active
yes
total
—
9.8 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
CWE-502 — Deserialization of Untrusted Data
2026-07-16

D3FEND Countermeasures

Defensive techniques inferred by MITRE D3FEND from the underlying weakness (CWE-502) — general hardening and detection guidance for this weakness class, not a vendor patch for this specific CVE.

KEV Catalog Status

2026-07-16
2026-07-19
Unknown

Listed By

SourceDateRecord
CISA KEV 2026-07-16 source record →
CISA Vulnrichment 2026-07-16 source record →

Referenced in Advisories

DateAdvisoryIssuer
2026-07-23 2026-009: Critical Vulnerabilities in Microsoft SharePoint CERT-EU
2026-07-16 CISA Adds Three Known Exploited Vulnerabilities to Catalog CISA
2026-07-15 Microsoft Releases July 2026 Security Updates JPCERT/CC
2026-07-14 CISA Urges SharePoint Hardening After New Exploitations CISA

Weaponization Timeline — Offensive & Testing Tools

DateToolEvidence qualityReference
2026-08-13 Nuclei Direct — curated exploit code CVE-2026-58644.yaml

Evidence tiers are explained on the About page — a merged Metasploit module is far stronger evidence than a distro package mention.

External References