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Vulnerability record · CVE-2026-56191 · published 24 July 2026

CVE-2026-56191: Microsoft exchange online improper authentication vulnerability

Microsoft · Exchange Online

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

10.0 CVSS 3.1 Critical EPSS 0.90% · top 41.9% CWE-287 · Improper authentication
10.0CVSS 3.1 base score
0.90%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
29 Jul 2026Last modified by NVD

Description

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

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2026-65801Microsoft exchange online server-side request forgery (ssrf) vulnerabilityServer-side request forgery (ssrf) in Microsoft Exchange Online allows an unauthorized attacker to elevate privileges over a network.EPSS 0.90%9.6CVE-2026-48582Microsoft exchange online missing authorization vulnerabilityMissing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.EPSS 0.69%8.8CVE-2026-54998Microsoft exchange online incorrect authorization vulnerabilityIncorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.EPSS 0.78%7.5CVE-2026-48579Microsoft exchange online improper authorization vulnerabilityImproper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.EPSS 1.00%7.5CVE-2026-42018JFrog Artifactory improper authentication leaks anonymous tokenJFrog Artifactory can return an internal anonymous-user token to an unauthenticated caller even when anonymous access is disabled. Because the token …KEVEPSS 9.8%analysed9.8CVE-2026-82329JFrog Artifactory improper authentication allows admin takeoverJFrog Artifactory contains an improper authentication weakness (CWE-287) that, under default configuration, may let an unauthenticated attacker with …KEVEPSS 14%analysed8.8CVE-2026-59822LiteLLM MCP endpoint auth bypass via OAuth2 passthrough fallbackLiteLLM's MCP Streamable HTTP endpoint, prior to 1.84.0, let an unauthenticated attacker send a fabricated Authorization header that triggered an OAu…KEVEPSS 0.84%analysed10.0CVE-2026-49869Kestra OSS auth bypass via path suffix match enables RCEKestra OSS AuthenticationFilter whitelists the public config endpoint using request.getPath().endsWith("/configs"), a suffix match instead of an exac…KEVEPSS 2.1%analysed

Source: NIST National Vulnerability Database (record CVE-2026-56191), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.