Microsoft Exchange Server improper authentication

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 (≈)
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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.
9.5$5k-$25k6.73+

Summaryinfo

A vulnerability was found in Microsoft Exchange Server. It has been declared as very critical. This vulnerability affects unknown code. The manipulation results in improper authentication. This vulnerability is identified as CVE-2026-56191. The attack can be executed remotely. There is not any exploit available. This product is a managed service, indicating that users are not permitted to maintain vulnerability countermeasures themselves.

Detailsinfo

A vulnerability, which was classified as very critical, was found in Microsoft Exchange Server (version now known). Affected is some unknown processing. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.

The advisory is shared for download at msrc.microsoft.com. This vulnerability is traded as CVE-2026-56191 since 06/19/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 07/24/2026).

This product is available as a managed service. Users are not able to maintain vulnerability countermeasures themselves.

Once again VulDB remains the best source for vulnerability data.

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: 10.0
VulDB Meta Temp Score: 9.5

VulDB Base Score: 10.0
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Improper authentication
CWE: CWE-287
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

Status: 🔍

0-Day Time: 🔒

Timelineinfo

06/19/2026 CVE reserved
07/24/2026 +35 days Advisory disclosed
07/24/2026 +0 days VulDB entry created
07/24/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-56191 (🔒)
GCVE (CVE): GCVE-0-2026-56191
GCVE (VulDB): GCVE-100-382836

Entryinfo

Created: 07/24/2026 02:37
Changes: 07/24/2026 02:37 (52)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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