CVE-2026-42517: e-Sushrut Information Disclosure Flaw

CVE-2026-42517 Overview

This vulnerability exists in e-Sushrut due to the use of reversible Base64 encoding for protecting sensitive data. An authenticated attacker could exploit this vulnerability by decoding and manipulating Base64-encoded parameters in the request URL to gain unauthorized access to sensitive information on the targeted system. The vulnerability is classified under CWE-639 (Authorization Bypass Through User-Controlled Key), indicating a fundamental flaw in how the application handles access control decisions.

Critical Impact

Authenticated attackers can decode and manipulate Base64-encoded URL parameters to access sensitive patient healthcare data and system information without proper authorization.

Affected Products

• e-Sushrut Healthcare Management System

Discovery Timeline

• April 29, 2026 - CVE-2026-42517 published to NVD
• April 29, 2026 - Last updated in NVD database

Technical Details for CVE-2026-42517

Vulnerability Analysis

This vulnerability stems from a critical cryptographic design flaw where e-Sushrut relies on Base64 encoding as a security mechanism for protecting sensitive data in URL parameters. Base64 is an encoding scheme, not an encryption method—it provides zero cryptographic protection and can be trivially reversed by any attacker with basic technical knowledge.

The authorization bypass (CWE-639) occurs because the application uses user-controlled, Base64-encoded values in request URLs to determine which resources a user can access. Since authenticated users can easily decode these parameters, modify the underlying values (such as patient IDs or record identifiers), re-encode them, and submit the manipulated request, they can access resources belonging to other users or escalate their access privileges.

Healthcare applications like e-Sushrut typically contain highly sensitive Protected Health Information (PHI), making this vulnerability particularly severe from a data privacy and regulatory compliance perspective.

Root Cause

The root cause is the improper use of Base64 encoding as a security control mechanism. The developers appear to have confused encoding with encryption, implementing a scheme that provides obfuscation rather than actual protection. Additionally, the application fails to implement proper server-side authorization checks to verify that authenticated users are permitted to access the specific resources they request—instead trusting the encoded URL parameters.

Attack Vector

The attack is network-based and requires authenticated access to the e-Sushrut application. An attacker would first authenticate with valid credentials (even low-privileged), then intercept requests containing Base64-encoded parameters. They would decode these parameters to understand the underlying data structure, modify values such as user IDs, record identifiers, or access tokens, re-encode the manipulated data, and submit the crafted request to access unauthorized resources.

The vulnerability is straightforward to exploit as Base64 decoding is available in countless online tools and programming libraries, requiring no specialized skills beyond basic web application knowledge.

Detection Methods for CVE-2026-42517

Indicators of Compromise

• Unusual patterns of access to patient records by single user accounts accessing data outside their normal scope
• Rapid sequential requests with varying Base64-encoded parameters from the same authenticated session
• Access logs showing users viewing records for patients not assigned to their care or department
• Error logs indicating failed access attempts followed by successful unauthorized access patterns

Detection Strategies

• Implement application-layer logging to track all resource access attempts and correlate them with user authorization levels
• Deploy web application firewall (WAF) rules to detect parameter tampering patterns in Base64-encoded URL segments
• Configure SIEM alerts for anomalous access patterns where users access resources outside their normal behavioral baseline
• Establish user behavior analytics to identify accounts exhibiting horizontal privilege escalation patterns

Monitoring Recommendations

• Enable detailed access logging for all sensitive data endpoints within e-Sushrut
• Monitor for high-frequency requests with varying encoded parameters from individual sessions
• Implement real-time alerting for access to patient records outside of established care relationships
• Review authentication and authorization logs regularly for evidence of parameter manipulation attempts

How to Mitigate CVE-2026-42517

Immediate Actions Required

• Review all URL parameters in e-Sushrut that use Base64 encoding and implement proper server-side authorization checks
• Audit access logs for evidence of exploitation—look for users accessing records outside their authorized scope
• Apply any available vendor patches or updates from the e-Sushrut development team
• Consider temporarily restricting network access to the application while implementing fixes
• Review the CERT-IN Vulnerability Note CIVN-2026-0207 for official guidance

Patch Information

Organizations using e-Sushrut should consult the official CERT-IN Vulnerability Note CIVN-2026-0207 for specific remediation guidance and any available patches. Contact the e-Sushrut vendor directly for security updates addressing this vulnerability.

Workarounds

• Implement server-side authorization checks that validate user permissions against requested resources independent of URL parameters
• Replace Base64-encoded identifiers with cryptographically secure, non-guessable tokens that are validated server-side
• Deploy a web application firewall (WAF) to inspect and block requests with manipulated parameters
• Implement rate limiting on sensitive data access endpoints to slow exploitation attempts
• Consider network segmentation to limit access to the e-Sushrut application to only authorized network segments

Organizations should implement robust access control mechanisms following the principle of least privilege. Server-side authorization verification should occur for every sensitive data request, ensuring that the authenticated user has explicit permission to access the specific resource regardless of what parameters are submitted in the request.