Type Vulnerability
Microsoft is announcing the availability of the security updates for Microsoft Office for Mac.
Microsoft · Memory corruption
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network
CVE-2026-70291
What this means
This is rated critical severity (9.8 out of 10). There is no confirmed exploitation of it yet. Ask IT whether Microsoft 365 Apps, Microsoft Microsoft 365 and Microsoft Office 2021, and 1 more are in your estate, and treat that as the priority.
Full vendor description
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Scoring and exploitation
9.8/ 10
CVSS 3.1 base scoreCritical
Exploitable over the network without any account, and no one has to click or open anything. High impact on confidentiality, integrity and availability.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitability
Longer bar: easier to attack
Attack vectorNetworkAV:N
Attack complexityLowAC:L
Privileges requiredNonePR:N
User interactionNoneUI:N
ScopeUnchangedS:U
Impact
Longer bar: more harm
ConfidentialityHighC:H
IntegrityHighI:H
AvailabilityHighA:H
- ~1.3% estimated chance of attack in 30 daysModel estimate (): a probability signal, not confirmed exploitation
- Exploited in the wild
- Not confirmed in the
- Not reported
Weaknesses
CWE-122
Affected products ()
- Microsoft 365 Apps
- Microsoft Microsoft 365
- Microsoft Office 2021
- Microsoft Office 2024
Show the raw CPE strings (9)
- cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*
- cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*
- cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:*
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:*
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:*
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:*
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:*
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:*
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:*
References
1 link from the CVE record, grouped by site; the vendor's advisory comes first.
msrc.microsoft.com1 linkVendor advisory
- CVE-2026-70291 (opens in a new tab)Vendor Advisory
Related feed events
- Type Vulnerability
Microsoft is publishing 1,413 own-product vulnerabilities on October 2026 Patch Tuesday, including 1,102 in Windows. Known-exploited catalogue reports exploitation in the wild.