Summary

CVE-2025-14847 is a high-severity memory disclosure vulnerability in MongoDB Server’s handling of zlib-compressed network protocol headers.

An unauthenticated remote attacker with network access to a MongoDB instance can trigger the server to return uninitialised heap memory, potentially exposing credentials, API keys, and sensitive application data.

A public exploit, MongoBleed, has been released and validated by independent researchers, significantly lowering the bar for mass exploitation.

Affected Systems and/or Applications

This impacts both:

• MongoDB Server (self-hosted): on-prem, IaaS, containers, Kubernetes
• MongoDB Atlas (managed service)
  (Vendor reports Atlas was patched prior to disclosure; risk is primarily self-hosted)

Affected Versions

• 8.2.x: 8.2.0 – 8.2.2
• 8.0.x: 8.0.0 – 8.0.16
• 7.0.x: 7.0.0 – 7.0.26
• 6.0.x: 6.0.0 – 6.0.26
• 5.0.x: 5.0.0 – 5.0.31
• 4.4.x: 4.4.0 – 4.4.29
• All MongoDB Server 4.2.x (EoL, no patches)
• All MongoDB Server 4.0.x (EoL, no patches)
• All MongoDB Server 3.6.x (EoL, no patches)

Any self-hosted instance in these ranges with zlib compression enabled and network-reachable should be considered vulnerable.

Technical Details

MongoDB supports optional compression (including zlib) for network messages between clients and servers.
The vulnerability arises from incorrect validation of length fields in zlib-compressed protocol headers.

Root Cause

• MongoDB trusts length values from the wire protocol
• Crafted packets can cause a mismatch between declared and actual decompressed length
• The server reads past the intended buffer
• Uninitialised heap memory is returned in responses

Key Properties

• Pre-authentication: no login required
• Low complexity: only network access and zlib compression required
• Impact scope: arbitrary fragments of server memory

Potentially Leaked Data

• Database usernames and passwords (often cleartext)
• Cloud credentials (e.g. AWS access keys)
• API tokens, OAuth/JWTs
• Recent query results
• PII, financial data, and application secrets

There is confirmation that the MongoBleed exploit actively searches memory leaks for database passwords and AWS keys.

While the vulnerability is technically an information disclosure, it can rapidly lead to:

• Full database compromise
• Bulk data exfiltration
• Lateral movement and cloud privilege escalation

Indicators of Compromise

• Unusual network traffic patterns:
  • 3–5× normal connection volume
  • Upwards of 100,000+ connections observed in PoCs
• Unexpected data leakage from MongoDB
• Lack of client metadata once connections are established

Mitigation

Upgrade to one of the following patched MongoDB Server versions:

• MongoDB Server v8.2.3 or later
• MongoDB Server v8.0.17 or later
• MongoDB Server v7.0.28 or later
• MongoDB Server v6.0.27 or later
• MongoDB Server v5.0.32 or later
• MongoDB Server v4.4.30 or later

MongoDB Atlas

MongoDB reports Atlas clusters were patched prior to public disclosure.
No tenant action is required for this CVE, though standard hardening is still advised.

Workarounds

1. Disable zlib Compression (CVE-2025-14847 Specific)

Disable zlib and use safer compressors (snappy, zstd), or disable compression entirely.

Command-line

mongod --setParameter networkMessageCompressors=snappy,zstd # or: mongod --setParameter networkMessageCompressors=disabled

Configuration File (YAML)

net: compression: compressors: snappy,zstd # or: # compressors: disabled

This is an effective interim mitigation, but does not replace patching.

2. Restrict Network Exposure

• Ensure MongoDB is not directly reachable from the internet
• Restrict access to:
  • Private networks / VPNs
  • Known application subnets
  • Bastion hosts (firewalls, security groups)

Given the historically high number of internet-exposed MongoDB instances, any public exposure should be treated as high risk.

3. Enforce Authentication and TLS

While authentication does not prevent exploitation (pre-auth bug), enforcing:

• Strong authentication (SCRAM, x.509)
• TLS for all client connections

is critical to reducing follow-on attack impact.

Recommended Actions for Cloud / Platform Teams

Inventory

Enumerate all MongoDB instances across:

• On-prem
• Public cloud (all accounts)
• Containers / Kubernetes
• Dev, test, staging, and production

Exposure Review

Identify:

• Internet-facing instances
• Instances reachable from broad internal networks

Prioritisation

• Tier 1: Internet-facing or partner-accessible
• Tier 2: Broad internal access
• Tier 3: Isolated test / lab

Remediation

• Patch to fixed versions
• Disable zlib as interim control where needed
• Enforce network restrictions, TLS, and authentication

Secrets Hygiene

After patching, rotate:

• Database credentials
• Application secrets
• Cloud credentials that may have touched MongoDB memory

What the Cyber Fusion Center Is Doing

The Cyber Fusion Center (CFC) is actively monitoring the situation and will update this advisory as new information becomes available.

References

• MongoDB Jira Issue SERVER-115508
• GitHub – CYBERDUDEBIVASH-MONGODB-DETECTOR-v2026
• GitHub – CVE-2025-14847-PoC
• GitHub – mongobleed-exploit-CVE-2025-14847
• https://blog.cyberdesserts.com/mongobleed-cve-2025-14847/
• https://orca.security/resources/blog/cve-2025-14847-mongodb-heap-memory-leak/
• https://www.bleepingcomputer.com/news/security/mongodb-warns-admins-to-patch-severe-vulnerability-immediately/
• https://www.thehackerwire.com/mongodb-server-heap-info-leak-cve-2025-14847/
• https://doublepulsar.com/merry-christmas-day-have-a-mongodb-security-incident-9537f54289eb

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