CVE-2025-48935: Deno Auth Bypass Vulnerability

CVE-2025-48935 Overview

CVE-2025-48935 is an authorization bypass vulnerability in the Deno runtime environment for JavaScript, TypeScript, and WebAssembly. This security flaw allows attackers to circumvent Deno's permission-based security model, specifically bypassing read/write database permission checks through the use of the ATTACH DATABASE SQL statement.

Deno is designed with a security-first approach, implementing a granular permission system that restricts access to filesystem, network, and other sensitive resources. This vulnerability undermines that security model by providing an unexpected pathway to access database resources without the required permissions.

Critical Impact

Attackers can bypass Deno's permission security model to read and write database files without authorization, potentially leading to unauthorized data access, modification, or exfiltration.

Affected Products

• Deno versions 2.2.0 through 2.2.4
• Applications using Deno with SQLite database functionality
• Systems relying on Deno's permission model for database access control

Discovery Timeline

• June 4, 2025 - CVE-2025-48935 published to NVD
• July 2, 2025 - Last updated in NVD database

Technical Details for CVE-2025-48935

Vulnerability Analysis

This vulnerability is classified as CWE-863 (Incorrect Authorization), indicating a fundamental flaw in how Deno validates permissions for database operations. The core issue lies in an incomplete permission check when handling the SQLite ATTACH DATABASE command.

Deno's permission system is designed to require explicit authorization before an application can read or write to files on the filesystem. However, the ATTACH DATABASE statement provides a mechanism to associate additional database files with an existing SQLite connection. The permission validation logic failed to properly intercept and validate this specific database operation path.

When an attacker uses ATTACH DATABASE, they can specify an arbitrary file path to attach as a secondary database. Since the permission check was not implemented for this code path, the operation succeeds regardless of whether the application has been granted the appropriate --allow-read or --allow-write permissions.

Root Cause

The root cause of this vulnerability is incomplete permission enforcement in Deno's SQLite integration layer. When the ATTACH DATABASE statement is executed, the runtime fails to invoke its standard filesystem permission checks before allowing the database file operation. This represents a gap in the security boundary where the permission model was not applied consistently across all database-related operations.

The vulnerability stems from an assumption that all file access would go through monitored code paths, overlooking the fact that SQLite's ATTACH DATABASE functionality creates an alternative route to filesystem access.

Attack Vector

The attack vector is network-based and requires no user interaction or special privileges. An attacker can exploit this vulnerability in scenarios where:

1. A Deno application processes user-controlled SQL queries or database operations
2. The application is intentionally run with restricted permissions to limit file access
3. The attacker crafts a malicious ATTACH DATABASE statement targeting sensitive files

The vulnerability can be exploited by constructing SQL statements that leverage ATTACH DATABASE to access files outside the intended permission scope. For example, an attacker could attach a database file in a protected directory that the application should not have access to, then query or modify its contents.

For detailed technical information and the specific code changes, see the GitHub Security Advisory and the patch commit.

Detection Methods for CVE-2025-48935

Indicators of Compromise

• Unexpected ATTACH DATABASE statements in application logs or SQL query logs
• Database connections accessing files outside designated data directories
• SQLite operations on files that should be protected by permission restrictions
• Anomalous file access patterns from Deno processes running with limited permissions

Detection Strategies

• Implement SQL query logging and monitoring for ATTACH DATABASE statements
• Review Deno application logs for permission-related warnings or unexpected database operations
• Conduct code audits to identify any user-controlled input that could influence database operations
• Deploy file integrity monitoring on sensitive database files and directories

Monitoring Recommendations

• Enable verbose logging for Deno applications processing database operations
• Monitor filesystem access patterns from Deno runtime processes
• Set up alerts for SQL statements containing ATTACH or DETACH keywords
• Implement application-level query filtering as a defense-in-depth measure

How to Mitigate CVE-2025-48935

Immediate Actions Required

• Upgrade Deno to version 2.2.5 or later immediately
• Audit all Deno applications for potential exposure to user-controlled SQL queries
• Review and restrict network access to affected applications until patched
• Implement input validation to sanitize or reject ATTACH DATABASE statements at the application level

Patch Information

The Deno development team has addressed this vulnerability in version 2.2.5. The fix ensures that proper permission checks are enforced when processing ATTACH DATABASE statements, closing the authorization bypass path.

The patch commit can be reviewed at the official Deno repository. Organizations should update to the patched version through their standard package management process.

Workarounds

• Implement application-level filtering to block or sanitize SQL statements containing ATTACH DATABASE
• Run affected applications in isolated environments with additional filesystem restrictions
• Use database connection wrappers that intercept and validate all SQL statements before execution
• Deploy network segmentation to limit the exposure of vulnerable Deno applications

# Upgrade Deno to patched version
deno upgrade --version 2.2.5

# Verify installed version
deno --version