Microsoft 365 Apps for Enterprise/Office buffer overflow

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.1$0-$5k0.00+

Summaryinfo

A vulnerability, which was classified as critical, was found in Microsoft 365 Apps for Enterprise and Office. Impacted is an unknown function. Executing a manipulation can lead to buffer overflow. This vulnerability is registered as CVE-2026-123380. It is possible to launch the attack remotely. No exploit is available. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Microsoft 365 Apps for Enterprise and Office (affected version not known). It has been declared as critical. This vulnerability affects some unknown functionality. The manipulation with an unknown input leads to a buffer overflow vulnerability. The CWE definition for the vulnerability is CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

The advisory is shared for download at msrc.microsoft.com. This vulnerability was named CVE-2026-123380 since 11/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 11/10/2026).

Applying a patch is able to eliminate this problem.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.1
VulDB Meta Temp Score: 7.1

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 8.8
CNA Vector (microsoft): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Buffer overflow
CWE: CWE-120 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Timelineinfo

11/05/2026 CVE reserved
11/10/2026 +5 days Advisory disclosed
11/10/2026 +0 days VulDB entry created
11/10/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CNA: microsoft
CVE: CVE-2026-123380 (🔒)

GCVE (CVE): GCVE-0-2026-123380
GCVE (VulDB): GCVE-100-435220

Entryinfo

Created: 11/10/2026 23:46
Changes: 11/10/2026 23:46 (61)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

Discussion

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