Executive Summary

CVE-2025-66391 is a vulnerability in Citrix Cloud through November 10, 2025, where an account with read-only access can trigger workflows intended for write operations.

Specifically, a read-only user can manipulate server responses to bypass client-side authorization checks, allowing them to initiate privileged actions such as sending one-time passwords (OTPs) to an attacker-controlled email address during password reset attempts.

This occurs because authorization is enforced only on the client side, enabling attackers to interact with sensitive identity management features despite lacking proper permissions.

While full account takeover was not achieved in testing, the ability to send OTPs to attacker-controlled addresses represents a partial compromise of account security and may lead to full privilege escalation, especially when non-SSO accounts are used.

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Impact Analysis

This vulnerability can impact you by allowing an attacker with only read-only access to trigger sensitive workflows, such as password resets, and redirect one-time passwords to their own email address.

This partial compromise of account security could lead to unauthorized access or privilege escalation, especially in environments using non-SSO accounts.

Such unauthorized actions undermine the integrity of identity management and could facilitate further attacks or account takeovers.

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Detection Guidance

Detection of CVE-2025-66391 involves monitoring for unauthorized attempts to trigger privileged workflows by read-only accounts, such as password reset requests that result in one-time passwords being sent to unexpected or attacker-controlled email addresses.

Since the exploit abuses client-side authorization checks and manipulates server responses, network detection can focus on unusual API calls or requests from read-only accounts attempting write operations.

Specific commands are not provided in the available resources, but general approaches include reviewing logs for password reset attempts initiated by read-only users and monitoring outbound emails for OTPs sent to suspicious addresses.

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Mitigation Strategies

Immediate mitigation steps include enforcing backend authorization checks to ensure that only properly privileged accounts can initiate write operations such as password resets.

Reject unauthorized requests early in the workflow and strengthen state and session handling mechanisms to prevent exploitation of client-side authorization weaknesses.

Additionally, avoid using non-SSO accounts where possible, as these are more vulnerable to privilege escalation through this exploit.

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Compliance Impact

The vulnerability in Citrix Cloud allows a read-only user to trigger workflows for privileged actions, such as sending one-time passwords (OTPs) to attacker-controlled email addresses. This unauthorized access to identity management features, including password resets and email changes, can lead to partial compromise of account security and potential privilege escalation.

Such unauthorized access and potential data exposure could negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict controls on access to personal and sensitive information, as well as robust authentication and authorization mechanisms to protect user data.

Failure to prevent unauthorized password resets and OTP disclosures may result in violations of data protection principles, increasing the risk of data breaches and non-compliance with regulatory requirements.

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