CVE-2025-0755: MongoDB Libbson Buffer Overflow Vulnerability

CVE-2025-0755 Overview

CVE-2025-0755 is a heap-based buffer overflow vulnerability affecting the MongoDB C driver library (libbson). The various bson_append functions in the library are susceptible to buffer overflow when performing operations that could result in a final BSON document exceeding the maximum allowable size (INT32_MAX). Successful exploitation results in a segmentation fault and potential application crash, causing a denial of service condition.

Critical Impact

This vulnerability enables remote attackers to crash applications using the affected MongoDB C driver library by crafting malicious input that triggers a heap-based buffer overflow, leading to denial of service.

Affected Products

• MongoDB libbson versions prior to 1.27.5
• MongoDB Server v8.0 versions prior to 8.0.1
• MongoDB Server v7.0 versions prior to 7.0.16

Discovery Timeline

• 2025-03-18 - CVE-2025-0755 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-0755

Vulnerability Analysis

This heap-based buffer overflow (CWE-122) vulnerability exists in the MongoDB C driver library's BSON document handling functions. The bson_append family of functions fails to properly validate the cumulative size of BSON documents being constructed. When document operations would cause the resulting BSON document to exceed INT32_MAX (2,147,483,647 bytes), the buffer overflow occurs without proper boundary checking.

The vulnerability is exploitable over the network without requiring authentication or user interaction, making it accessible to unauthenticated remote attackers. The impact is limited to availability, as the overflow results in a segmentation fault that crashes the affected application rather than allowing arbitrary code execution.

Root Cause

The root cause lies in insufficient size validation within the bson_append functions. When multiple append operations are performed on a BSON document, the library does not adequately verify that the cumulative document size remains within the INT32_MAX boundary. This missing bounds check allows memory to be written beyond allocated buffer boundaries, triggering a segmentation fault.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Sending specially crafted requests to an application using the vulnerable libbson library
2. Constructing input that causes multiple BSON append operations
3. Triggering operations that would result in a BSON document exceeding INT32_MAX bytes
4. Causing the heap-based buffer overflow and subsequent application crash

The vulnerability affects applications that process untrusted BSON data or allow users to construct large BSON documents through API interactions.

Detection Methods for CVE-2025-0755

Indicators of Compromise

• Unexpected application crashes with segmentation fault signals in MongoDB-related processes
• Core dumps showing crashes in bson_append family functions within the libbson library
• Memory access violations in processes linked against vulnerable libbson versions
• Repeated service restarts due to crashes in MongoDB client applications

Detection Strategies

• Monitor system logs for segmentation fault events in applications using MongoDB C driver
• Implement application crash monitoring for services utilizing libbson
• Deploy memory safety monitoring tools to detect heap overflow attempts
• Use runtime application self-protection (RASP) solutions to identify abnormal memory access patterns

Monitoring Recommendations

• Configure centralized logging to capture crash events from MongoDB client applications
• Set up alerts for abnormal BSON document sizes in application telemetry
• Monitor for unusual patterns in MongoDB connection attempts that could indicate exploitation attempts
• Implement SentinelOne endpoint protection to detect and alert on exploitation behavior

How to Mitigate CVE-2025-0755

Immediate Actions Required

• Upgrade libbson to version 1.27.5 or later immediately
• Update MongoDB Server v8.0 installations to version 8.0.1 or later
• Update MongoDB Server v7.0 installations to version 7.0.16 or later
• Review and inventory all applications using the MongoDB C driver library

Patch Information

MongoDB has released patches addressing this vulnerability. Updated versions include:

• libbson: Version 1.27.5 and later include the fix
• MongoDB Server 8.0: Version 8.0.1 and later are patched
• MongoDB Server 7.0: Version 7.0.16 and later are patched

For detailed patch information, refer to the MongoDB C Driver Issue (CDRIVER-5601) and MongoDB Server Issue (SERVER-94461). Debian users should also review the Debian LTS Security Announcements for distribution-specific updates.

Workarounds

• Implement input validation to limit the size of BSON documents before processing
• Deploy application-level controls to reject requests that could result in excessively large documents
• Use network segmentation to limit exposure of vulnerable applications to untrusted networks
• Consider deploying a Web Application Firewall (WAF) to filter malicious requests targeting MongoDB endpoints

# Verify installed libbson version
pkg-config --modversion libbson-1.0

# Check MongoDB Server version
mongod --version

# Update libbson on Debian/Ubuntu systems
sudo apt update && sudo apt install libbson-1.0-0

# Update MongoDB Server
sudo apt update && sudo apt install mongodb-org