CVE-2026-45659

CRITICALPre-NVD 8.89.0
EchelonGraph scoreHIGH confidence

“▲” beside the score: it is higher than the CVSS score beside it.

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2026-07-01), indicating real-world exploitation has been confirmed by US federal agencies. The CNA's CVSS baseline 8.8 retained for reference (NVD's own analysis pending). The 9.0 is the floor for confirmed exploitation, not an impact rating: this CVE's impact severity (EG Severity) is CVSS 8.8 HIGH under GitHub Security Advisory CVSS. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: CISA Known Exploited Vulnerabilities catalog, the CNA's CVSS, EPSS, GitHub Security Advisory
Exploited in the wild

Also known asEUVD-2026-31518 (ENISA EUVD) · GHSA-w3mh-jmwv-56f3 (GitHub Security Advisories)Source: ENISA EUVD

9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV) — the reason this is sooner than the SSVC decision on this page at low or medium mission impact
CISA-KEV: ExploitedEPSS PROB: 80%CVSS: 8.8Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

CVSS v3
8.8
EG Score
9.0CRITICALhigh confidence
EG Risk
80
EG Risk 80/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity88% × 45%
Impact severity (EG Severity): CVSS 8.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation100% × 40%
Fixed at 100% for a CISA KEV listing: EchelonGraph's rule.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Attend at medium and Act at high mission impact.
Exploitation active (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact.
EPSS PROB
80%
EPSS %ILE
99th
KEV
⚠ Exploited

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is the CISA KEV floor for confirmed exploitation, not an impact rating: its impact severity (EG Severity) is CVSS 8.8 HIGH.

EG Severity
8.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
80% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
CISA KEV and EG-KEV Tier 1 (exploited in the wild)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Attend at medium mission impactTrack at low, Attend at medium and Act at high mission impact.CISA BOD 26-04: 3 days & forensic triage if the affected system is publicly exposed; 14 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Attend at medium and Act at high mission impact.

A fix is available. Apply it within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact.

Exploitation active (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)3 days & forensic triage if the affected system is publicly exposed; 14 days if it is not.

The score's inputs: In CISA KEV yes (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

CISA required action“Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.”

Quoted verbatim from CISA's Known Exploited Vulnerabilities catalog. CISA directs it at US federal civilian executive branch agencies under Binding Operational Directive (BOD) 26-04, which replaced BOD 22-01 on 10 June 2026; it is not EchelonGraph's advice. CISA's notes: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659 · https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk · https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk · https://nvd.nist.gov/vuln/detail/CVE-2026-45659

Published

May 26, 2026

Last Modified

August 11, 2026

Advisory Details (1)

Auto-updated Nov 9, 2026
⚠️ Actively exploited (CISA KEV, CISA Vulnrichment). Patch available. Sources: microsoft.
Microsoft

Security Update Guide - Microsoft Security Response Center

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659

Vendor Advisories for CVE-2026-45659(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 64× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 1,504 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 1,404 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:29 UTCEchelonGraph re-scored
  2. 2026-11-13 16:29 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  3. 2026-11-12 14:20 UTCEchelonGraph re-scored
  4. 2026-11-12 14:20 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  5. 2026-11-11 16:39 UTCEPSS rescoreEPSS 80% · 99th percentile
  6. 2026-11-11 12:23 UTCEchelonGraph re-scored
  7. 2026-11-11 12:23 UTCVendor advisory
  8. 2026-11-11 12:23 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  9. 2026-11-10 16:44 UTCEPSS rescoreEPSS 80% · 99th percentile
  10. 2026-11-10 10:25 UTCEchelonGraph re-scored
  11. 2026-11-10 10:25 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  12. 2026-11-09 08:28 UTCEchelonGraph re-scored
  13. 2026-11-09 08:28 UTCVendor advisory
  14. 2026-11-09 08:28 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  15. 2026-11-08 06:31 UTCEchelonGraph re-scored
  16. 2026-11-08 06:31 UTCVendor advisory
  17. 2026-11-08 06:31 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  18. 2026-11-07 04:33 UTCEchelonGraph re-scored
  19. 2026-11-07 04:33 UTCVendor advisory
  20. 2026-11-07 04:33 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  21. 2026-11-06 16:38 UTCEPSS rescoreEPSS 80% · 99th percentile
  22. 2026-11-06 02:36 UTCEchelonGraph re-scored
  23. 2026-11-06 02:36 UTCVendor advisory
  24. 2026-11-06 02:36 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  25. 2026-11-05 00:39 UTCEchelonGraph re-scored
Show 75 more
  1. 2026-11-05 00:39 UTCVendor advisory
  2. 2026-11-05 00:39 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  3. 2026-11-04 16:35 UTCEPSS rescoreEPSS 80% · 99th percentile
  4. 2026-11-03 22:42 UTCEchelonGraph re-scored
  5. 2026-11-03 22:42 UTCVendor advisory
  6. 2026-11-03 22:42 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  7. 2026-11-02 20:45 UTCEchelonGraph re-scored
  8. 2026-11-02 20:45 UTCVendor advisory
  9. 2026-11-02 20:45 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  10. 2026-11-01 18:48 UTCEchelonGraph re-scored
  11. 2026-11-01 18:48 UTCVendor advisory
  12. 2026-11-01 18:48 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  13. 2026-10-31 16:50 UTCEchelonGraph re-scored
  14. 2026-10-31 16:50 UTCVendor advisory
  15. 2026-10-31 16:50 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  16. 2026-10-31 16:32 UTCEPSS rescoreEPSS 80% · 99th percentile
  17. 2026-10-30 14:53 UTCEchelonGraph re-scored
  18. 2026-10-30 14:53 UTCVendor advisory
  19. 2026-10-30 14:53 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  20. 2026-10-29 16:33 UTCEPSS rescoreEPSS 80% · 99th percentile
  21. 2026-10-29 12:56 UTCEchelonGraph re-scored
  22. 2026-10-29 12:56 UTCVendor advisory
  23. 2026-10-29 12:56 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  24. 2026-10-28 16:32 UTCEPSS rescoreEPSS 80% · 99th percentile
  25. 2026-10-28 10:59 UTCEchelonGraph re-scored
  26. 2026-10-28 10:59 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  27. 2026-10-27 09:01 UTCEchelonGraph re-scored
  28. 2026-10-27 09:01 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  29. 2026-10-26 16:31 UTCEPSS rescoreEPSS 80% · 99th percentile
  30. 2026-10-26 07:05 UTCEchelonGraph re-scored
  31. 2026-10-26 07:04 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  32. 2026-10-25 16:33 UTCEPSS rescoreEPSS 80% · 99th percentile
  33. 2026-10-25 14:26 UTCEchelonGraph re-scored
  34. 2026-10-25 05:05 UTCEchelonGraph re-scored
  35. 2026-10-25 05:05 UTCVendor advisory
  36. 2026-10-25 05:05 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  37. 2026-10-24 16:33 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  38. 2026-10-24 03:09 UTCEchelonGraph re-scored
  39. 2026-10-24 03:09 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  40. 2026-10-23 16:31 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  41. 2026-10-23 01:11 UTCEchelonGraph re-scored
  42. 2026-10-23 01:11 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  43. 2026-10-22 16:34 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  44. 2026-10-21 23:11 UTCEchelonGraph re-scored
  45. 2026-10-21 23:11 UTCVendor advisory
  46. 2026-10-21 23:11 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  47. 2026-10-21 16:33 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  48. 2026-10-20 21:13 UTCEchelonGraph re-scored
  49. 2026-10-20 21:13 UTCVendor advisory
  50. 2026-10-20 21:13 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  51. 2026-10-20 16:33 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  52. 2026-10-19 19:16 UTCEchelonGraph re-scored
  53. 2026-10-19 19:16 UTCVendor advisory
  54. 2026-10-19 19:15 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  55. 2026-10-19 16:32 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  56. 2026-10-18 17:17 UTCEchelonGraph re-scored
  57. 2026-10-18 17:17 UTCVendor advisory
  58. 2026-10-18 17:17 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  59. 2026-10-18 16:32 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  60. 2026-10-18 03:38 UTCEchelonGraph re-scored
  61. 2026-10-17 16:34 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  62. 2026-10-17 15:20 UTCEchelonGraph re-scored
  63. 2026-10-17 15:20 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  64. 2026-10-16 16:42 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  65. 2026-10-16 13:23 UTCEchelonGraph re-scored
  66. 2026-10-16 13:23 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  67. 2026-10-15 16:32 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  68. 2026-10-15 11:25 UTCEchelonGraph re-scored
  69. 2026-10-15 11:25 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  70. 2026-10-14 16:33 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  71. 2026-10-14 09:25 UTCEchelonGraph re-scored
  72. 2026-10-14 09:25 UTCGHSA enrichmentGHSA-w3mh-jmwv-56f3 · GitHub severity HIGH · GitHub CVSS 8.8
  73. 2026-10-13 16:34 UTCEPSS rescoreEPSS 2.7% · 85th percentile
  74. 2026-10-13 07:28 UTCEchelonGraph re-scored
  75. 2026-10-13 07:28 UTCVendor advisory

Frequently asked(6)

What is CVE-2026-45659?
CVE-2026-45659 is a critical-severity vulnerability; its CVE record was published on May 26, 2026. Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
When was CVE-2026-45659 made public?
CVE-2026-45659 was made public on May 21, 2026: that is the date its CVE record's CNA, Microsoft Corporation, gives for when the vulnerability was made public. The CVE record itself was published on May 26, 2026. EchelonGraph's copy of the record carries a last-modified date of August 11, 2026; the record at its source may have been updated since.
Is CVE-2026-45659 actively exploited?
Yes. CISA added CVE-2026-45659 to the Known Exploited Vulnerabilities catalog on July 1, 2026, affecting Microsoft SharePoint Server. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. A fix is available. Apply it.
What is the CVSS score of CVE-2026-45659?
CVE-2026-45659 has a CVSS base score of 8.8 (the CNA's own assessment, by microsoft; NVD's own analysis pending). EchelonGraph synthesises the CNA's CVSS + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
Which products are affected by CVE-2026-45659?
CVE-2026-45659 affects Microsoft SharePoint Server.
How do I remediate CVE-2026-45659?
A fix for CVE-2026-45659 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-45659 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-45659

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