CVE-2025-57052: Davegamble cJSON Information Disclosure

CVE-2025-57052 Overview

CVE-2025-57052 is a critical out-of-bounds read vulnerability affecting cJSON versions 1.5.0 through 1.7.18. The vulnerability exists in the decode_array_index_from_pointer function within cJSON_Utils.c, which fails to properly validate JSON pointer strings. This allows remote attackers to bypass array bounds checking and access restricted memory regions by supplying malformed JSON pointer strings containing alphanumeric characters.

cJSON is a lightweight C library widely used for parsing and generating JSON data, commonly integrated into embedded systems, IoT devices, and various applications requiring JSON processing capabilities.

Critical Impact

Remote attackers can exploit this vulnerability to read sensitive data from memory, potentially leading to information disclosure of cryptographic keys, authentication tokens, or other confidential information processed by the application.

Affected Products

• davegamble cjson versions 1.5.0 through 1.7.18

Discovery Timeline

• 2025-09-03 - CVE-2025-57052 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-57052

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), a memory safety issue that occurs when the software reads data past the intended buffer boundaries. The flaw resides in how cJSON processes JSON Pointer strings, specifically within the array index parsing logic.

The decode_array_index_from_pointer function is responsible for extracting numeric array indices from JSON Pointer reference tokens. When processing malformed pointer strings that contain unexpected alphanumeric characters, the function fails to properly validate the input before using the parsed index value to access array elements. This insufficient input validation allows an attacker to craft specially constructed JSON pointer strings that cause the library to read beyond the allocated array boundaries.

Root Cause

The root cause of this vulnerability is improper input validation in the JSON Pointer parsing code. The decode_array_index_from_pointer function in cJSON_Utils.c does not adequately verify that the reference token consists solely of valid numeric characters before converting it to an array index. When alphanumeric characters are present in positions that bypass the initial validation checks, the resulting index calculation can produce values that exceed the legitimate array bounds.

Attack Vector

This vulnerability is exploitable remotely over the network without requiring authentication or user interaction. An attacker can exploit this vulnerability by:

1. Sending a malicious JSON document to an application that uses the vulnerable cJSON library
2. Including a specially crafted JSON Pointer string with alphanumeric characters designed to bypass bounds checking
3. When the application processes the malformed pointer, it reads memory beyond the intended array boundaries
4. The attacker may retrieve sensitive data from adjacent memory locations through error messages, responses, or application behavior

The vulnerability can be triggered in any application that accepts JSON input and uses cJSON's pointer functionality to navigate JSON structures. For detailed technical analysis of the parsing vulnerability, refer to the X-0R Vulnerability Post.

Detection Methods for CVE-2025-57052

Indicators of Compromise

• Abnormal JSON parsing errors or crashes in applications using cJSON
• Unexpected memory access violations or segmentation faults during JSON processing
• Applications returning unexpected data or exhibiting memory corruption symptoms
• Log entries showing malformed JSON pointer processing attempts

Detection Strategies

• Implement application-layer monitoring for JSON requests containing unusual pointer syntax with alphanumeric characters in array index positions
• Deploy memory safety tools such as AddressSanitizer (ASan) to detect out-of-bounds read attempts in development and testing environments
• Monitor for process crashes or abnormal terminations in services that parse JSON input using cJSON
• Conduct static analysis of applications to identify usage of vulnerable cJSON versions

Monitoring Recommendations

• Enable verbose logging for JSON parsing operations to capture malformed input attempts
• Implement rate limiting on endpoints that accept JSON input to mitigate exploitation attempts
• Monitor system memory access patterns for anomalies that may indicate exploitation
• Set up alerts for application crashes related to JSON processing components

How to Mitigate CVE-2025-57052

Immediate Actions Required

• Identify all applications and systems using cJSON versions 1.5.0 through 1.7.18
• Prioritize patching systems that process untrusted JSON input from network sources
• Review application logs for evidence of exploitation attempts
• Consider implementing input validation at the application layer to sanitize JSON pointer strings before processing

Patch Information

Organizations should update to a patched version of cJSON that addresses this vulnerability. For specific patch availability and update instructions, consult the official cJSON repository and the Debian LTS Security Announcement for Debian-based systems.

When updating, ensure all dependent applications are tested for compatibility with the patched library version.

Workarounds

• Implement strict input validation to reject JSON pointer strings containing non-numeric characters in array index positions
• Restrict access to endpoints that process JSON input using cJSON to trusted sources only
• Deploy web application firewalls (WAF) with rules to detect and block malformed JSON pointer patterns
• Run applications using cJSON in sandboxed environments to limit the impact of potential memory disclosure

# Example: Check installed cJSON version on Debian/Ubuntu systems
dpkg -l | grep cjson

# Update cJSON package on Debian-based systems
sudo apt-get update && sudo apt-get upgrade libcjson1