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CVE-2026-78520CriticalRCENetworkRevised 17 Sep

Microsoft Office Outlook Information Disclosure Vulnerability

MSRC advisory NVD CVE.org

Assessment

Out-of-bounds read in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

Severity
Critical
CVSS base score
6.5
Impact
Remote Code Execution
Exploitation detected
No known exploitation (MSRC assessment)
Exploitability
Exploitation Less Likely
Publicly disclosed
No (MSRC assessment)
EPSS · 30-day forecast
0.9%FIRST forecast dated 10 Nov 2026, for the following 30 days · FIRST percentile 60.6% · about EPSS
Customer action
Required: follow the MSRC remediation guidance
More details
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Public detection template
No Nuclei template is listed in the current collected catalog
Component
Microsoft Office Outlook
Weakness
CWE-125: Out-of-bounds Read
Issued by
Microsoft
Published
8 Sep 2026 · September 2026
Last revised
17 Sep 2026Microsoft is announcing the availability of the security updates for Microsoft Office for Mac. Customers running affected Mac software should install the update for their product to be protected from this vulnerability. Customers running other Microsoft Office software do not need to take any actio…
CVSS 3.1 base metricsRed raises the risk · green lowers it
Attack vector
NetworkAV:N
Attack complexity
LowAC:L
Privileges required
NonePR:N
User interaction
RequiredUI:R
Scope
UnchangedS:U
Confidentiality
HighC:H
Integrity
NoneI:N
Availability
NoneA:N

Updates that fix it

1 KB
KBTypeApplies toOther CVEs
KB5002923 Security UpdateMicrosoft Word 2016 (32-bit edition), Microsoft Word 2016 (64-bit edition)All CVEs in KB5002923

Affected products

Microsoft Office
13 affected products

What changed

  1. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  3. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  4. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  5. Detection template: No Nuclei template listed · Customer action: Required: apply the update → Required: follow the MSRC remediation guidance · Public disclosure: No → No (MSRC assessment) · Exploitation detected: Not reported by MSRC → No known exploitation (MSRC assessment)
  6. Detection template: Unknown: exploit-code evidence is incomplete or retained → No Nuclei template listed · CISA KEV: Unknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  7. Detection template: No Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained · CISA KEV: Not listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
Page history

Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.

Cite this version
Field-level log (61)

Up to 100 recent field edits are shown; older edits may be outside retention.

  1. 10 Nov 2026 · 18:32:11 UTC EPSS0.9%; scored 9 Nov 2026 → 0.9%; scored 10 Nov 2026
  2. 9 Nov 2026 · 22:24:37 UTC EPSS0.9%; scored 8 Nov 2026 → 0.9%; scored 9 Nov 2026
  3. 8 Nov 2026 · 15:16:05 UTC EPSS0.9%; scored 7 Nov 2026 → 0.9%; scored 8 Nov 2026
  4. 7 Nov 2026 · 16:12:44 UTC EPSS0.9%; scored 6 Nov 2026 → 0.9%; scored 7 Nov 2026
  5. 6 Nov 2026 · 19:15:37 UTC EPSS0.9%; scored 5 Nov 2026 → 0.9%; scored 6 Nov 2026
  6. 6 Nov 2026 · 17:32:22 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  7. 6 Nov 2026 · 17:32:22 UTC Source coverage: public-exploit-codeIncomplete → Current
  8. 6 Nov 2026 · 17:32:22 UTC Source coverage: first-epssIncomplete → Current
  9. 6 Nov 2026 · 17:32:22 UTC Source coverage: msrc-cvrfIncomplete → Current
  10. 6 Nov 2026 · 16:31:02 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  11. 6 Nov 2026 · 16:31:02 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  12. 6 Nov 2026 · 16:31:02 UTC Source coverage: first-epssCurrent → Incomplete
  13. 6 Nov 2026 · 16:31:02 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  14. 5 Nov 2026 · 23:42:03 UTC EPSS0.9%; scored 4 Nov 2026 → 0.9%; scored 5 Nov 2026
  15. 5 Nov 2026 · 02:36:20 UTC EPSS0.9%; scored 3 Nov 2026 → 0.9%; scored 4 Nov 2026
  16. 4 Nov 2026 · 03:04:37 UTC EPSS0.9%; scored 2 Nov 2026 → 0.9%; scored 3 Nov 2026
  17. 3 Nov 2026 · 01:53:36 UTC EPSS0.9%; scored 1 Nov 2026 → 0.9%; scored 2 Nov 2026
  18. 2 Nov 2026 · 17:30:39 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  19. 2 Nov 2026 · 17:30:39 UTC Source coverage: public-exploit-codeIncomplete → Current
  20. 2 Nov 2026 · 17:30:39 UTC Source coverage: first-epssIncomplete → Current
  21. 2 Nov 2026 · 17:30:39 UTC Source coverage: msrc-cvrfIncomplete → Current
  22. 2 Nov 2026 · 16:27:39 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  23. 2 Nov 2026 · 16:27:39 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  24. 2 Nov 2026 · 16:27:39 UTC Source coverage: first-epssCurrent → Incomplete
  25. 2 Nov 2026 · 16:27:39 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  26. 2 Nov 2026 · 00:36:51 UTC EPSS0.9%; scored 31 Oct 2026 → 0.9%; scored 1 Nov 2026
  27. 31 Oct 2026 · 18:22:15 UTC EPSS0.9%; scored 30 Oct 2026 → 0.9%; scored 31 Oct 2026
  28. 30 Oct 2026 · 18:02:45 UTC EPSS0.9%; scored 29 Oct 2026 → 0.9%; scored 30 Oct 2026
  29. 29 Oct 2026 · 20:19:26 UTC Public detection templateNo Nuclei template listed
  30. 29 Oct 2026 · 20:19:26 UTC Customer actionRequired: apply the update → Required: follow the MSRC remediation guidance
  31. 29 Oct 2026 · 20:19:26 UTC Publicly disclosedNo → No (MSRC assessment)
  32. 29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → No known exploitation (MSRC assessment)
  33. 29 Oct 2026 · 18:33:30 UTC EPSS0.9%; scored 28 Oct 2026 → 0.9%; scored 29 Oct 2026
  34. 28 Oct 2026 · 20:00:33 UTC EPSS0.9%; scored 27 Oct 2026 → 0.9%; scored 28 Oct 2026
  35. 27 Oct 2026 · 15:48:13 UTC EPSS0.9%; scored 26 Oct 2026 → 0.9%; scored 27 Oct 2026
  36. 26 Oct 2026 · 23:57:09 UTC EPSS0.9%; scored 25 Oct 2026 → 0.9%; scored 26 Oct 2026
  37. 25 Oct 2026 · 17:12:51 UTC EPSS0.9%; scored 24 Oct 2026 → 0.9%; scored 25 Oct 2026
  38. 25 Oct 2026 · 01:34:18 UTC EPSS0.9%; scored 23 Oct 2026 → 0.9%; scored 24 Oct 2026
  39. 23 Oct 2026 · 15:51:28 UTC EPSS0.9%; scored 22 Oct 2026 → 0.9%; scored 23 Oct 2026
  40. 23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
  41. 23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  42. 23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
  43. 23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
  44. 23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
  45. 23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
  46. 23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
  47. 23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
  48. 23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  49. 23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
  50. 23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
  51. 23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  52. 22 Oct 2026 · 17:33:15 UTC EPSS0.9%; scored 21 Oct 2026 → 0.9%; scored 22 Oct 2026
  53. 21 Oct 2026 · 21:47:24 UTC EPSS0.9%; scored 20 Oct 2026 → 0.9%; scored 21 Oct 2026
  54. 20 Oct 2026 · 20:53:31 UTC EPSS0.9%; scored 19 Oct 2026 → 0.9%; scored 20 Oct 2026
  55. 19 Oct 2026 · 15:12:40 UTC EPSS0.9%; scored 18 Oct 2026 → 0.9%; scored 19 Oct 2026
  56. 18 Oct 2026 · 14:54:30 UTC EPSS0.9%; scored 16 Oct 2026 → 0.9%; scored 18 Oct 2026
  57. 18 Oct 2026 · 14:54:30 UTC Link: September 2026/security?release=2026-Sep#cves
  58. 16 Oct 2026 · 16:13:25 UTC EPSS0.9%; scored 15 Oct 2026 → 0.9%; scored 16 Oct 2026
  59. 15 Oct 2026 · 21:30:54 UTC EPSS0.9%; scored 14 Oct 2026 → 0.9%; scored 15 Oct 2026
  60. 15 Oct 2026 · 01:07:54 UTC EPSS0.9%; scored 13 Oct 2026 → 0.9%; scored 14 Oct 2026
  61. 14 Oct 2026 · 11:22:42 UTC Source coverage: msrc-cvrfIncomplete → Current

Explore global source statements, affected packages and advisory history for CVE-2026-78520. The catalog has a separate collection scope from Microsoft release records.

cve-program · CVE-2026-78520

Published

Microsoft 365 Apps for Enterprise

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft 365 Apps for Enterprise",
                    "platforms": [
                        "32-bit Systems",
                        "x64-based Systems"
                    ],
                    "versions": [
                        {
                            "version": "16.0.1",
                            "lessThan": "16.0.20326.20138",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office 2019

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office 2019",
                    "platforms": [
                        "32-bit Systems",
                        "x64-based Systems"
                    ],
                    "versions": [
                        {
                            "version": "19.0.0",
                            "lessThan": "16.0.10417.20207",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office 365 for Mac

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office 365 for Mac",
                    "versions": [
                        {
                            "version": "1.0.0",
                            "lessThan": "16.113.26091433",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office LTSC 2021

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office LTSC 2021",
                    "platforms": [
                        "32-bit Systems",
                        "x64-based Systems"
                    ],
                    "versions": [
                        {
                            "version": "16.0.1",
                            "lessThan": "16.0.14334.20906",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office LTSC 2024

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office LTSC 2024",
                    "platforms": [
                        "32-bit Systems",
                        "x64-based Systems"
                    ],
                    "versions": [
                        {
                            "version": "16.0.0",
                            "lessThan": "16.0.17932.20976",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office LTSC for Mac 2021

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office LTSC for Mac 2021",
                    "versions": [
                        {
                            "version": "16.0.1",
                            "lessThan": "16.113.26091433",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Office LTSC for Mac 2024

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Office LTSC for Mac 2024",
                    "versions": [
                        {
                            "version": "16.0.0",
                            "lessThan": "16.113.26091433",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Microsoft Word 2016

Vendor product

Original vendor version evidence · not evaluated as a NuGet range
{
                    "vendor": "Microsoft",
                    "product": "Microsoft Word 2016",
                    "platforms": [
                        "32-bit Systems",
                        "x64-based Systems"
                    ],
                    "versions": [
                        {
                            "version": "16.0.1",
                            "lessThan": "16.0.5569.1000",
                            "versionType": "custom",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON

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Sources read 11 Nov 03:41 UTC · 275 of 275 readable · 273 fully read · documentation 469/469 current

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