MongoDB Server Pre-Auth Heap Memory Disclosure via Zlib Compressed Protocol Header Length Mismatch (CVE-2025-14847)
Executive & SecOps Summary
SECOPS ASSESSMENTAll MongoDB Server versions v3.6+, v4.0+, v4.2+, and versions prior to v4.4.30, v5.0.32, v6.0.27, v7.0.28, v8.0.17, and v8.2.3
An unauthenticated remote attacker can read uninitialized heap memory by sending crafted Zlib compressed protocol headers, potentially exposing highly sensitive system and session data
Immediately upgrade MongoDB Server to the respective patched release versions (v4.4.30, v5.0.32, v6.0.27, v7.0.28, v8.0.17, v8.2.3, or later)
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update your MongoDB Server packages to the latest secure releases using your operating system's package manager.
# For Ubuntu/Debian-based systems
sudo apt-get update
sudo apt-get --only-upgrade install -y mongodb-org mongodb-org-server
# For RHEL/CentOS/Rocky Linux-based systems
sudo yum clean all
sudo yum update -y mongodb-org-server2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict network binding in the MongoDB configuration file (/etc/mongod.conf) and enforce strict firewall rules to block untrusted traffic.
# 1. Restrict bindIp in /etc/mongod.conf to localhost or trusted internal IPs only
# Edit the net section as follows:
# net:
# port: 27017
# bindIp: 127.0.0.1,10.0.0.5
# 2. Restrict access to port 27017 using UFW firewall
sudo ufw deny 27017/tcp
sudo ufw allow from 10.0.0.0/24 to any port 27017 proto tcp
sudo ufw reload3. Log Audit & IoC Verification Commands
Verify the running MongoDB version and inspect the logs for anomalous connection terminations or protocol errors.
# 1. Check the currently running MongoDB version
mongod --version | grep 'db version'
# 2. Scan MongoDB logs for abnormal connection drops or protocol anomalies
# (Adjust the log path according to your environment configuration)
sudo grep -Ei 'connection.*ended|protocol.*error|invalid.*length' /var/log/mongodb/mongod.log | tail -n 50Block Exploits Instantly with Managed Virtual Patching Rules
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2025-14847, publicly referred to as 'MongoBleed') exists in the network communication protocol handling of MongoDB Server. MongoDB supports the OP_COMPRESSED message structure to optimize data transmission between clients and the server, utilizing compression algorithms such as Zlib. The root cause of this flaw is a length field validation mismatch (CWE-130) within the Zlib compressed protocol headers. When there is a discrepancy between the actual decompressed data size and the length specified in the header, the server fails to validate this mismatch, allocating and copying memory in a way that exposes uninitialized heap memory back to the client.
2. Exploitation Mechanics & Attack Scenario
An unauthenticated remote attacker can establish a direct TCP connection to the MongoDB service port (default: 27017) and transmit a specially crafted OP_COMPRESSED packet. This packet contains a manipulated header where the declared decompressed length is significantly larger than the actual compressed payload. Upon receiving this request, the MongoDB server allocates a heap buffer corresponding to the spoofed decompressed length. Because the actual decompressed data does not fill the allocated buffer, the remaining space retains residual data previously stored in that heap memory segment. The server then transmits this entire buffer back to the client, allowing the attacker to read raw heap memory contents without authentication.
3. Infrastructure & Business Impact
This vulnerability has been assigned a CVSS score of 7.5 (High) and is actively cataloged in the CISA KEV (Known Exploited Vulnerabilities) list, indicating active exploitation in the wild. Successful exploitation allows attackers to extract highly sensitive business and infrastructure data residing in the heap memory, including database credentials, active session tokens, internal query structures, and cached database records. Since this occurs during the pre-authentication phase, any MongoDB instance exposed to the public internet is at extreme risk of data exfiltration.
Official Vendor Advisories & References
Mismatched length fields in Zlib compressed protocol headers may allow a read of uninitialized heap memory by an unauthenticated client. This issue affects all MongoDB Server v7.0 prior to 7.0.28 versions, MongoDB Server v8.0 versions prior to 8.0.17, MongoDB Server v8.2 versions prior to 8.2.3, 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 greater than or equal to 4.2.0, MongoDB Server v4.0 versions greater than or equal to 4.0.0, and MongoDB Server v3.6 versions greater than or equal to 3.6.0.
Frequently Asked SecOps Questions (CVE-2025-14847)
FAQQ1. How critical is CVE-2025-14847 and is it actively exploited in the wild?
CVE-2025-14847 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 83.2%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2025-14847?
Primary impacted vendors include mongodb across mongodb_server. Scope summary: MongoDB Server versions v3.6.0 and newer, v4.0.0 and newer, v4.2.0 and newer, and prior to v4.4.30, v5.0.32, v6.0.27, v7.0.28, v8.0.17, and v8.2.3
Q3. What temporary mitigations or workarounds exist for CVE-2025-14847 before patching?
[Mitigation] Immediately upgrade MongoDB Server to the respective patched release versions (v4.4.30, v5.0.32, v6.0.27, v7.0.28, v8.0.17, v8.2.3, or later) Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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