Microsoft 365 Copilots Business Chat Downstream injection

CVSS Meta Temp Score
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Current Exploit Price (≈)
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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.
6.3$0-$5k0.00

Summaryinfo

A vulnerability was found in Microsoft 365 Copilots Business Chat and classified as critical. Impacted is an unknown function of the component Downstream Component. Executing a manipulation can lead to injection. This vulnerability is registered as CVE-2026-26164. It is possible to launch the attack remotely. No exploit is available. This product is a managed service, which means users themselves cannot handle vulnerability countermeasures.

Detailsinfo

A vulnerability was found in Microsoft 365 Copilots Business Chat (the affected version is unknown). It has been declared as critical. This vulnerability affects an unknown code of the component Downstream Component. The manipulation with an unknown input leads to a injection vulnerability. The CWE definition for the vulnerability is CWE-74. The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. As an impact it is known to affect confidentiality. CVE summarizes:

Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.

The advisory is shared for download at msrc.microsoft.com. This vulnerability was named CVE-2026-26164 since 02/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. 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 06/04/2026). The MITRE ATT&CK project declares the attack technique as T1055.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-28446) and CERT Bund (WID-SEC-2026-1411). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

  • Microsoft 365 Copilot

Productinfo

Type

Vendor

Name

License

Managed Service

  • yes

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.4
VulDB Meta Temp Score: 6.3

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.5
CNA Vector (microsoft): 🔒

CVSSv2info

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

Exploitinginfo

Class: Injection
CWE: CWE-74 / CWE-707 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Status: 🔍

0-Day Time: 🔒

Timelineinfo

02/11/2026 CVE reserved
05/08/2026 +85 days Advisory disclosed
05/08/2026 +0 days VulDB entry created
06/04/2026 +27 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-26164 (🔒)
GCVE (CVE): GCVE-0-2026-26164
GCVE (VulDB): GCVE-100-361960
EUVD: 🔒
CERT Bund: WID-SEC-2026-1411 - Microsoft 365 Copilot Business Chat: Mehrere Schwachstellen ermöglichen Offenlegung von Informationen

Entryinfo

Created: 05/08/2026 05:45
Updated: 06/04/2026 14:17
Changes: 05/08/2026 05:45 (63), 05/11/2026 08:06 (7), 05/24/2026 02:53 (1), 06/04/2026 14:17 (1)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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