MongoBleed (CVE-2025-14847) is a critical unauthenticated memory leak in MongoDB Server affecting versions back to 3.6. Details on the flaw, exploits, patches, and mitigation steps
As of December 27, 2025, a severe security vulnerability known as MongoBleed (CVE-2025-14847) has been disclosed in MongoDB Server, enabling unauthenticated attackers to extract sensitive data from server memory. The flaw, stemming from improper handling of zlib-compressed network messages, affects a wide range of versions and has prompted urgent patching warnings. Discussions are trending on social media with hashtags like #MongoBleed and #CVE202514847, as security experts highlight the ease of exploitation and potential for data exposure.
What Is the MongoBleed Vulnerability?
MongoBleed exploits a flaw in MongoDB’s zlib decompression process. Attackers send specially crafted compressed payloads with mismatched length fields, causing the server to allocate a large buffer but only partially fill it with decompressed data. The server then treats the entire buffer—including uninitialized heap memory—as valid BSON content, leaking fragments in responses.
This unauthenticated attack can reveal sensitive information such as credentials, session tokens, personally identifiable information (PII), system metrics, or cached query data. While primarily an information disclosure issue (CVSS 7.5-8.7, High severity), leaked secrets could enable further compromises.
Affected Versions and Patches
The vulnerability impacts nearly all MongoDB Server versions released over the past decade, including:
- 8.2.x prior to 8.2.3
- 8.0.x prior to 8.0.17
- 7.0.x prior to 7.0.28
- 6.0.x prior to 6.0.27
- 5.0.x prior to 5.0.32
- 4.4.x prior to 4.4.30
- All 4.2.x, 4.0.x, and 3.6.x series
MongoDB has released patches in the latest versions. Administrators should upgrade immediately. As a temporary workaround, disable zlib compression by configuring networkMessageCompressors or net.compression.compressors to exclude zlib (e.g., use snappy or zstd instead).
Exploitation and Proof-of-Concept
A public proof-of-concept exploit, dubbed “mongobleed,” was released shortly after disclosure, allowing automated scanning and memory dumping. The tool probes different offsets to extract fragments, potentially leaking thousands of bytes per run. Security researchers note that internet-exposed instances are at high risk, with scanning likely already underway.
Detection is challenging, as attacks generate high connection rates detectable in MongoDB logs but often not forwarded to SIEM systems.
Industry Reactions and Recommendations
The disclosure has sparked alarm in the cybersecurity community, with experts comparing it to past “Bleed” vulnerabilities like Heartbleed or CitrixBleed due to its simplicity and impact. Vendors like Orca Security, OX Security, and RunZero have issued alerts, emphasizing exposure checks for internet-facing databases.
Recommendations include:
- Prioritize patching vulnerable instances.
- Restrict network access (avoid 0.0.0.0/0 bindings; use VPC peering or allowlists).
- Monitor for anomalous connection patterns.
- Scan environments for affected versions.
MongoDB Atlas users should verify auto-upgrades, as managed services may already be protected.
Conclusion
The MongoBleed vulnerability underscores the risks of exposed database services and the need for prompt security updates. With public exploits available, organizations running MongoDB should treat this as a critical priority to prevent potential data breaches.
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