CVE-2025-14847: MongoDB Information Disclosure Vulnerability

CVE-2025-14847 Overview

CVE-2025-14847, also known as "MongoBleed," is a high-severity memory information disclosure vulnerability affecting MongoDB Server. The vulnerability exists in the handling of Zlib compressed protocol headers, where mismatched length fields allow an unauthenticated client to read uninitialized heap memory. This pre-authentication memory disclosure flaw can expose sensitive information stored in server memory without requiring any credentials.

Critical Impact

This vulnerability is actively exploited in the wild and has been added to the CISA Known Exploited Vulnerabilities catalog. Unauthenticated attackers can remotely extract sensitive data from MongoDB server heap memory, potentially exposing credentials, encryption keys, and other confidential information.

Affected Products

• MongoDB Server v8.2 versions prior to 8.2.3
• MongoDB Server v8.0 versions prior to 8.0.17
• MongoDB Server v7.0 versions prior to 7.0.28
• MongoDB Server v6.0 versions prior to 6.0.27
• MongoDB Server v5.0 versions prior to 5.0.32
• MongoDB Server v4.4 versions prior to 4.4.30
• MongoDB Server v4.2 versions 4.2.0 and later (no patch available)
• MongoDB Server v4.0 versions 4.0.0 and later (no patch available)
• MongoDB Server v3.6 versions 3.6.0 and later (no patch available)

Discovery Timeline

• 2025-12-19 - CVE-2025-14847 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-14847

Vulnerability Analysis

This vulnerability stems from improper length checking in the OP_COMPRESSED message handler within MongoDB Server. When processing Zlib-compressed protocol messages, the server fails to properly validate the relationship between the declared uncompressed size and the actual decompressed data length. This mismatch creates a condition where the server allocates a buffer based on one length value but reads data using a different, larger length value, resulting in out-of-bounds read access to uninitialized heap memory.

The vulnerability is classified under CWE-130 (Improper Handling of Length Parameter Inconsistency), which describes scenarios where software receives input with inconsistent length specifications that lead to memory safety violations.

Root Cause

The root cause lies in the MongoDB wire protocol's handling of compressed messages. The OP_COMPRESSED opcode allows clients to send compressed payloads with metadata indicating both the compressed and uncompressed sizes. The vulnerability occurs when the server trusts the client-supplied uncompressed length field without verifying it matches the actual size of the decompressed data from the Zlib stream. An attacker can craft a malicious OP_COMPRESSED message with an inflated uncompressed length value, causing the server to read beyond the legitimate decompressed data into adjacent heap memory regions.

Attack Vector

The attack vector is network-based and requires no authentication, making it particularly dangerous for internet-facing MongoDB instances. An attacker can exploit this vulnerability by:

1. Establishing a TCP connection to the MongoDB port (default 27017)
2. Sending a specially crafted OP_COMPRESSED message with mismatched length fields
3. The server decompresses the payload and attempts to read the declared (inflated) length
4. Uninitialized heap memory contents are included in the server's response
5. The attacker receives portions of server memory potentially containing sensitive data

The pre-authentication nature of this vulnerability means attackers can extract memory contents without valid credentials. Depending on server activity and memory state, leaked data may include authentication credentials, session tokens, database content fragments, or cryptographic material.

Detection Methods for CVE-2025-14847

Indicators of Compromise

• Unusual OP_COMPRESSED messages with length field discrepancies in MongoDB network traffic
• Abnormal connection patterns from unknown sources sending malformed protocol messages
• MongoDB server logs showing compression-related errors or unexpected disconnections
• Network traffic analysis revealing responses larger than expected for compressed operations
• Connection attempts from known malicious IP addresses associated with this exploit

Detection Strategies

• Deploy network intrusion detection rules to identify malformed OP_COMPRESSED packets with mismatched length fields
• Monitor MongoDB logs for decompression errors or protocol violations from unauthenticated sessions
• Implement deep packet inspection on MongoDB wire protocol traffic at network boundaries
• Use the Vicarius Detection Script to scan for vulnerable MongoDB instances
• Enable MongoDB auditing to track connection attempts and protocol-level anomalies

Monitoring Recommendations

• Configure alerting for MongoDB connections from untrusted networks or unexpected geographic locations
• Monitor for reconnaissance activity targeting MongoDB default port 27017
• Implement baseline analysis for MongoDB traffic volume to detect data exfiltration attempts
• Review firewall logs for connection attempts to MongoDB from known exploit infrastructure
• Correlate MongoDB access logs with threat intelligence feeds containing CVE-2025-14847 indicators

How to Mitigate CVE-2025-14847

Immediate Actions Required

• Upgrade MongoDB Server to patched versions immediately: 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32, or 4.4.30
• For MongoDB versions 4.2, 4.0, and 3.6, plan urgent migration to supported versions as no patches are available
• Restrict network access to MongoDB instances using firewall rules to allow only trusted IP addresses
• Implement authentication requirements and disable anonymous access if not already configured
• Review MongoDB logs for evidence of exploitation attempts prior to patching

Patch Information

MongoDB has released security patches addressing this vulnerability across supported versions. Organizations should apply the following minimum versions:

Detailed patch information is available in the MongoDB Jira Ticket SERVER-115508. For additional mitigation guidance, refer to the Vicarius Mitigation Script.

Workarounds

• Disable network compression by setting net.compression.compressors to none in the MongoDB configuration
• Place MongoDB servers behind a reverse proxy or VPN to limit direct network exposure
• Implement network segmentation to isolate MongoDB instances from untrusted networks
• Use firewall rules to restrict MongoDB port access to application servers only
• Enable TLS/SSL with client certificate authentication to add an authentication layer before protocol handling

# MongoDB configuration to disable compression as a workaround
# Add to mongod.conf

net:
  compression:
    compressors: none
  bindIp: 127.0.0.1  # Restrict to localhost or trusted IPs only
  port: 27017

# Restart MongoDB after configuration change
# systemctl restart mongod