CVE-2026-78510Patch(microsoft / 365_apps)

LOWCVSS 8.4 · 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

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

1.0/ 10 priority

Sources & remediation

Weakness type (CWE)
CWE-122

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

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_2016
  • office_2019

Threat summary

  • Patch or workaround signal is available
  • 4 mentions across 4 observed days
  • Momentum state: stable

What's happening

  • Patch or workaround mentioned in 2 signals
  • Technical details provided in 3 signals
  • Disclosure: 2 classified signals
  • Peaked 3d ago at 1 mentions (2026-09-08); latest day: 1
  • 4 total mentions across 4 days

Affected systems

Vendors
Products
365_appsmicrosoft_365office_2016office_2019office_2021office_2024

1 version affected across 6 products

Deep dive

Activity timeline4 mentions / 4d
00111Mentions · 2026-09-08: 1Mentions · 2026-09-09: 1Mentions · 2026-09-10: 1Mentions · 2026-09-24: 1Patch / Workaround · 2026-09-08: 1Patch / Workaround · 2026-09-09: 1Technical Details · 2026-09-08: 1Technical Details · 2026-09-09: 1Technical Details · 2026-09-10: 109-0809-0909-1009-24
Signal classification2 categories
Patch
250.0%
Disclosure
250.0%
Referenced assets6 URLs
Classification over time
DateTotalLabels
2026-09-081
Patch1
2026-09-091
Patch1
2026-09-101
Disclosure1
2026-09-241
Disclosure1
Full discourse4 posts
  • Haifei Li@HaifeiLi
    Patch

    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 tweet announces three new Microsoft Office/Outlook CVEs, details a zero‑click RCE in Outlook's preview pane, urges users to apply the patches, and mentions a detection system for such attacks.

    115164117.0K
    8.9K followersView on X
  • Haifei Li@HaifeiLi
    Disclosure

    Update: MSRC has updated the title for CVE-2026-78510 per my request (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78510), still didn't specifically say Outlook (and Outlook Preview Pane).. but well.. https://x.com/HaifeiLi/status/2097403487609073826

    Post summary

    The text discusses an update to the CVE-2026-78510 title by MSRC at the user's request, focusing on clarifying its description without mentioning PoCs, exploits, patches, or active exploitation. The classification is Disclosure due to the focus on CVE entry updates rather than actionable exploitation or remediation.

    0501943.2K
    8.9K followersView on X
  • 🕳@sekurlsa_pw
    Disclosure

    @grondern Microsoft always calls this RCE. See for example this one in Word: https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2026-78510 "An unauthenticated attacker could exploit this vulnerability by crafting a malicious RTF file. If a user opens the file (....)"

    Post summary

    The tweet refers to Microsoft's advisory for CVE-2026-78510, labeling it as an RCE triggered by a crafted RTF file; it provides no PoC, exploit code, patch or active exploitation details.

    10121714
    2.7K followersView on X
  • Atlas Threat Monitoring@ThreatAtlas
    Patch

    Unpatched vulnerabilities don't stay hidden on our atlas. #CVE CRITICAL VULNERABILITY DETECTED CVE ID → CVE-2026-78510 Vendor → Microsoft Severity → Critical — CVSS 9.8 Product → Office 2021 Date → 2026-09-08 A critical vulnerability (Heap-based Buffer Overflow) has been disclosed affecting Office 2021. Patch immediately. Powered by @Brandefense #ThreatIntel #CyberSecurity #CVE #Microsoft

    Post summary

    The post announces a critical heap-based buffer overflow in Microsoft Office 2021 (CVE-2026-78510, CVSS 9.8) and urges users to patch immediately.

    00001124
    343 followersView on X
CPE platform detail13 entries

13 of 13 entries

PartVendorProductVersionTarget SWTarget HW
Appmicrosoft365_apps--x64
Appmicrosoft365_apps--x86
Appmicrosoftmicrosoft_365-macos-
Appmicrosoftoffice_2016--x64
Appmicrosoftoffice_2016--x86
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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