CVE-2026-56191

⛔ critical

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

CVSS Score

10.0

Critical

EPSS Score

0.7

Exploit Probability

Published Date

2026-07-24

First Seen: 2026-07-31

This CVE is Extremely High Risk - more severe than 100.0% of all 340,405 vulnerabilities in our database.

Top 5% most severe

Severity Percentile

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

YES

Can be exploited automatically

💥 Technical Impact

Total

Complete system compromise possible

SSVC data provided by CISA

Last Modified 2026-07-29

Source NVD 🔗

CVSS Vector 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CWE IDs (Weakness Types)

CWE-287

📦 Affected Products 1

Vendor	Product	Status	Affected Versions
microsoft	exchange_online	Affected	v-

🔗 References 1

🔗 Related CVEs 3

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-54998	⚠️ high	8.8	0.6	Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.	2026-07-02
CVE-2026-48582	⛔ critical	9.6	0.4	Missing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.	2026-06-19
CVE-2026-48579	⛔ critical	9.1	1.0	Improper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a netwo...	2026-06-04

These CVEs affect the same products