CVE-2026-78507Disclosure(microsoft / 365_apps)

LOWCVSS 8.8 · HIGH

Signal is active with 1 mentions in latest observed window

Immediate actions

  • Patch microsoft 365_apps systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD description

Use after free in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

1.0/ 10 priority

Sources & remediation

Weakness type (CWE)
CWE-416

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

NONE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

  • 365_apps
  • microsoft_365
  • office_2019
  • office_2021

Threat summary

  • Patch or workaround signal is available
  • 1 mentions across 1 observed day

What's happening

  • Patch or workaround mentioned in 1 signal
  • Technical details provided in 1 signal
  • Disclosure: 1 classified signal
  • 1 total mentions across 1 day

Affected systems

Vendors
Products
365_appsmicrosoft_365office_2019office_2021office_2024

1 version affected across 5 products

Deep dive

Activity timeline1 mentions / 1d
00111Mentions · 2026-09-08: 1Patch / Workaround · 2026-09-08: 1Technical Details · 2026-09-08: 109-08
Signal classification1 categories
Disclosure
1100.0%
Referenced assets4 URLs
Full discourse1 post
  • Haifei Li@HaifeiLi
    Disclosure

    This Microsoft Patch Tuesday, among with the historical 974 (!) bugs patched, I contributed three. - Microsoft Word Remote Code Execution Vulnerability (CVE-2026-78510) * https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78510 - Microsoft Office Outlook Remote Code Execution Vulnerability (CVE-2026-78509) https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509 - Microsoft Office Word Remote Code Execution Vulnerability (CVE-2026-78507) https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78507 For me, the most notable one is the CVE-2026-78510, the Microsoft Security Update Guide page's title is quite misleading as it didn't even say it affects Outlook. In fact, it's a zero-click RCE (or someone like to call it "half-click") on Microsoft Outlook affecting the Preview Pane, means the bug could be triggered as long as the user previews or opens the email on Outlook. I'm communicating with MSRC to hopefully address the misleading webpage. I recommend patching it sooner rather than later. Btw, if you're worrying about potential Outlook zero-click/half-click 0day attacks, I've put significant efforts in my @EXPMON_ system (https://pub.expmon.com) where it should be good at detecting such advanced attacks. It accepts email formats (.msg, .eml) and it checks deeply for various attack vectors! #PatchTuesday #OfficeSecurity #Outlook #zeroday #0day #EmailSecurity

    Post summary

    The post announces the Patch Tuesday CVEs for Microsoft Word and Outlook, highlights a zero‑click RCE in Outlook’s Preview Pane, urges immediate patching, and mentions a detection system for such attacks.

    115164117.0K
    8.9K followersView on X
CPE platform detail11 entries

11 of 11 entries

PartVendorProductVersionTarget SWTarget HW
Appmicrosoft365_apps--x64
Appmicrosoft365_apps--x86
Appmicrosoftmicrosoft_365-macos-
Appmicrosoftoffice_2019--x64
Appmicrosoftoffice_2019--x86
Appmicrosoftoffice_2021--x64
Appmicrosoftoffice_2021--x86
Appmicrosoftoffice_2021-macos-
Appmicrosoftoffice_2024--x64
Appmicrosoftoffice_2024--x86
Appmicrosoftoffice_2024-macos-

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