CVE-2026-41103: Microsoft Confluence SAML SSO Privilege Escalation

CVE-2026-41103 Overview

CVE-2026-41103 is a privilege escalation vulnerability in the Microsoft SSO Plugin for Atlassian Jira and Confluence. The flaw stems from an incorrect implementation of an authentication algorithm, classified as [CWE-303: Incorrect Implementation of Authentication Algorithm]. An unauthenticated attacker can exploit the weakness over the network to elevate privileges without user interaction. Microsoft published the advisory on May 12, 2026, and the issue affects both microsoft:confluence_saml_sso and microsoft:jira_saml_sso components.

Critical Impact
Remote, unauthenticated attackers can bypass SAML-based single sign-on validation and gain elevated access to Jira and Confluence instances, exposing source code, tickets, internal documentation, and administrative functionality.

Affected Products

Microsoft Confluence SAML SSO Plugin (microsoft:confluence_saml_sso)
Microsoft Jira SAML SSO Plugin (microsoft:jira_saml_sso)
Atlassian Jira and Confluence deployments using the Microsoft SSO Plugin for authentication

Discovery Timeline

2026-05-12 - CVE-2026-41103 published to NVD
2026-05-16 - Last updated in NVD database

Technical Details for CVE-2026-41103

Vulnerability Analysis

The vulnerability resides in the authentication algorithm used by the Microsoft SSO Plugin to validate SAML assertions during sign-on to Jira and Confluence. An incorrect implementation allows an attacker to satisfy the authentication check without presenting valid credentials. Because the plugin governs federated identity for the underlying Atlassian application, a successful bypass yields the privileges of the impersonated account.

The attack requires no privileges and no user interaction. Network-adjacent access to the SSO endpoint is sufficient to attempt exploitation. Microsoft classifies the issue under [CWE-303] alongside an additional NVD-CWE-Other mapping, indicating that the algorithmic flaw is the root authentication weakness. The current EPSS probability is 0.132%.

Root Cause

The plugin's authentication routine fails to correctly enforce the cryptographic and logical checks required by the SAML protocol. Common faults in this class include improper signature verification, missing audience or issuer validation, mishandling of XML canonicalization, or accepting assertions that fail integrity checks. The result is that forged or replayed authentication material is accepted as legitimate.

Attack Vector

An attacker reaches the affected SSO endpoint over the network and submits a crafted SAML response or authentication request. The plugin's flawed verification logic accepts the input and issues a session bound to a privileged identity. From there the attacker interacts with Jira or Confluence as that user, accessing protected projects, spaces, and administrative APIs. No verified proof-of-concept code is published as of the advisory date; refer to the Microsoft CVE-2026-41103 Advisory for vendor-supplied technical details.

Detection Methods for CVE-2026-41103

Indicators of Compromise

SAML authentication events for high-privilege accounts originating from unfamiliar IP addresses or autonomous systems.
Successful logins to Jira or Confluence without a corresponding identity provider authentication event in upstream Entra ID or AD FS logs.
New or modified administrator-level permissions in Jira or Confluence audit logs shortly after an SSO session is established.

Detection Strategies

Correlate Jira and Confluence application logs with identity provider sign-in logs to detect SSO sessions that lack a matching upstream authentication.
Alert on SAML assertions with unexpected issuers, audiences, or signature properties reaching the SSO plugin endpoint.
Monitor for anomalous administrative actions, such as user role changes, plugin installations, or bulk data exports following SSO sign-in.

Monitoring Recommendations

Forward Atlassian application logs, reverse proxy access logs, and identity provider logs to a centralized SIEM for cross-source correlation.
Baseline normal SSO sign-in patterns per user and geography, then alert on deviations such as impossible travel or new device fingerprints.
Track outbound API usage from Jira and Confluence service accounts to identify data staging that may follow privilege escalation.

How to Mitigate CVE-2026-41103

Immediate Actions Required

Apply the fixed version of the Microsoft SSO Plugin for Jira and Confluence referenced in the Microsoft CVE-2026-41103 Advisory.
Inventory all Jira and Confluence instances that use the Microsoft SSO Plugin and confirm patch status for each deployment.
Rotate session tokens, API tokens, and administrative credentials on affected systems after patching.
Review Jira and Confluence audit logs for unauthorized administrative changes since the plugin was deployed.

Patch Information

Microsoft has published guidance and a fixed plugin version through the Microsoft Security Response Center advisory. Administrators should consult the advisory for the specific plugin build that remediates the authentication algorithm flaw and follow Atlassian Marketplace update procedures to deploy it across both Jira and Confluence environments.

Workarounds

Temporarily disable the Microsoft SSO Plugin and require direct authentication or an alternative SAML provider until the patch is applied.
Restrict network access to the Jira and Confluence SSO endpoints to trusted corporate ranges or VPN gateways.
Enforce step-up authentication or conditional access policies at the identity provider for administrative Jira and Confluence groups.

bash

# Configuration example: restrict SSO endpoint access at the reverse proxy
# (nginx example - replace with your trusted source ranges)
location /plugins/servlet/samlsso {
    allow 10.0.0.0/8;
    allow 192.168.0.0/16;
    deny all;
    proxy_pass http://atlassian_backend;
}