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CVE-2026-78501CriticalInformation DisclosureNetworkRevised 13 Oct

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

MSRC advisory NVD CVE.org

Assessment

Improper neutralization of special elements used in a command ('command injection') in Microsoft 365 Copilot's Business Chat allows an unauthorized attacker to disclose information over a network.

Severity
Critical
CVSS base score
8.6
Impact
Information Disclosure
Exploitation detected
No known exploitation (MSRC assessment)
Exploitability
Not assessed
Publicly disclosed
No (MSRC assessment)
EPSS · 30-day forecast
0.5%FIRST forecast dated 10 Nov 2026, for the following 30 days · FIRST percentile 45.8% · about EPSS
Customer action
Not required (service-side fix)
More details
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 365 Copilot's Business Chat
Weakness
CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')
Issued by
Microsoft
Published
17 Sep 2026 · September 2026
Last revised
13 Oct 2026Updated the CVSS User Interaction metric from Required (UI:R) to None (UI:N). The CVSS base score has increased to 8.6. This is an informational change only. No customer action is required.
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
NoneUI:N
Scope
ChangedS:C
Confidentiality
HighC:H
Integrity
NoneI:N
Availability
NoneA:N

Updates that fix it

0 KBs

No KB listed

No KB update is listed in the collected MSRC record. Check the MSRC advisory for product releases and other remedies.

Affected products

Apps
1 affected product
  • Microsoft 365 Copilot's Business Chat

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 · 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
  8. Publisher revision note: Updated an acknowledgement. This is an informational change only. → Updated the CVSS User Interaction metric from Required (UI:R) to None (UI:N). The CVSS base score has increased to 8.6. This is an informational change only. No customer action is required. · CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C → CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C · CVSS score: 7.4 → 8.6
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 (64)

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

  1. 10 Nov 2026 · 18:32:11 UTC EPSS0.5%; scored 9 Nov 2026 → 0.5%; scored 10 Nov 2026
  2. 9 Nov 2026 · 22:24:37 UTC EPSS0.5%; scored 8 Nov 2026 → 0.5%; scored 9 Nov 2026
  3. 8 Nov 2026 · 15:16:05 UTC EPSS0.5%; scored 7 Nov 2026 → 0.5%; scored 8 Nov 2026
  4. 7 Nov 2026 · 16:12:44 UTC EPSS0.5%; scored 6 Nov 2026 → 0.5%; scored 7 Nov 2026
  5. 6 Nov 2026 · 19:15:37 UTC EPSS0.5%; scored 5 Nov 2026 → 0.5%; 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 EPSS0.5%; scored 4 Nov 2026 → 0.5%; scored 5 Nov 2026
  15. 5 Nov 2026 · 02:36:20 UTC EPSS0.5%; scored 3 Nov 2026 → 0.5%; scored 4 Nov 2026
  16. 4 Nov 2026 · 03:04:37 UTC EPSS0.5%; scored 2 Nov 2026 → 0.5%; scored 3 Nov 2026
  17. 3 Nov 2026 · 01:53:36 UTC EPSS0.5%; scored 1 Nov 2026 → 0.5%; 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 EPSS0.5%; scored 31 Oct 2026 → 0.5%; scored 1 Nov 2026
  27. 31 Oct 2026 · 18:22:15 UTC EPSS0.5%; scored 30 Oct 2026 → 0.5%; scored 31 Oct 2026
  28. 30 Oct 2026 · 18:02:45 UTC EPSS0.5%; scored 29 Oct 2026 → 0.5%; 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 Publicly disclosedNo → No (MSRC assessment)
  31. 29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → No known exploitation (MSRC assessment)
  32. 29 Oct 2026 · 18:33:30 UTC EPSS0.5%; scored 28 Oct 2026 → 0.5%; scored 29 Oct 2026
  33. 28 Oct 2026 · 20:00:33 UTC EPSS0.5%; scored 27 Oct 2026 → 0.5%; scored 28 Oct 2026
  34. 27 Oct 2026 · 15:48:13 UTC EPSS0.5%; scored 26 Oct 2026 → 0.5%; scored 27 Oct 2026
  35. 26 Oct 2026 · 23:57:09 UTC EPSS0.5%; scored 25 Oct 2026 → 0.5%; scored 26 Oct 2026
  36. 25 Oct 2026 · 17:12:51 UTC EPSS0.5%; scored 24 Oct 2026 → 0.5%; scored 25 Oct 2026
  37. 25 Oct 2026 · 01:34:18 UTC EPSS0.5%; scored 23 Oct 2026 → 0.5%; scored 24 Oct 2026
  38. 23 Oct 2026 · 15:51:28 UTC EPSS0.5%; scored 22 Oct 2026 → 0.5%; scored 23 Oct 2026
  39. 23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
  40. 23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  41. 23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
  42. 23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
  43. 23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
  44. 23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
  45. 23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
  46. 23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
  47. 23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  48. 23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
  49. 23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
  50. 23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  51. 22 Oct 2026 · 17:33:15 UTC EPSS0.5%; scored 21 Oct 2026 → 0.5%; scored 22 Oct 2026
  52. 21 Oct 2026 · 21:47:24 UTC EPSS0.5%; scored 20 Oct 2026 → 0.5%; scored 21 Oct 2026
  53. 20 Oct 2026 · 20:53:31 UTC EPSS0.5%; scored 19 Oct 2026 → 0.5%; scored 20 Oct 2026
  54. 19 Oct 2026 · 15:12:40 UTC EPSS0.5%; scored 18 Oct 2026 → 0.5%; scored 19 Oct 2026
  55. 18 Oct 2026 · 14:54:30 UTC EPSS0.5%; scored 16 Oct 2026 → 0.5%; scored 18 Oct 2026
  56. 18 Oct 2026 · 14:54:30 UTC Link: September 2026/security?release=2026-Sep#cves
  57. 16 Oct 2026 · 16:13:25 UTC EPSS0.5%; scored 15 Oct 2026 → 0.5%; scored 16 Oct 2026
  58. 15 Oct 2026 · 21:30:54 UTC EPSS0.5%; scored 14 Oct 2026 → 0.5%; scored 15 Oct 2026
  59. 15 Oct 2026 · 01:07:54 UTC EPSS0.5%; scored 13 Oct 2026 → 0.5%; scored 14 Oct 2026
  60. 14 Oct 2026 · 15:58:54 UTC Revision noteUpdated an acknowledgement. This is an informational change only. → Updated the CVSS User Interaction metric from Required (UI:R) to None (UI:N). The CVSS base score has increased to 8.6. This is an informational change only. No customer action is required.
  61. 14 Oct 2026 · 15:58:54 UTC Last revised6 Oct 2026 07:00 UTC → 13 Oct 2026 07:00 UTC
  62. 14 Oct 2026 · 15:58:54 UTC CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C → CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C
  63. 14 Oct 2026 · 15:58:54 UTC CVSS base score7.4 → 8.6
  64. 14 Oct 2026 · 11:22:42 UTC Source coverage: msrc-cvrfIncomplete → Current

Explore global source statements, affected packages and advisory history for CVE-2026-78501. The catalog has a separate collection scope from Microsoft release records.

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Dated risk observations

Risk history is separate from CNA/OSV content history. Daily score drift is retained but only an upward crossing of 10% triggers the prediction change event.

Immutable source observations

4 recorded revisions

Each citation identifies one complete source statement. Source modification dates and the time this installation observed them are distinct. Latest history includes records historically associated by source identifiers; a removed alias is not a current equivalence claim. Exact citations show that source record's own earlier observations. Failed reads and unchanged polls do not rewrite history.

10 Nov 2026 23:21:22 UTC

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

cve-program · CVE-2026-78501 · Published

31 Oct 2026 18:04:47 UTC

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

cve-program · CVE-2026-78501 · Published

30 Oct 2026 22:45:26 UTC

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

cve-program · CVE-2026-78501 · Published

23 Oct 2026 15:48:27 UTC

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

cve-program · CVE-2026-78501 · Published

ChangeIntel

An IT change radar: releases, security, known issues, retirements, documentation changes, and service status from public sources. Every item links to supporting evidence; dates and statuses can change after they are read.

Sources read 12 Nov 02:22 UTC · 274 of 275 readable · 272 fully read · documentation 468/469 current

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