A high-severity vulnerability in MongoDB Server that allows unauthenticated remote attackers to siphon sensitive data from database memory.
Dubbed “MongoBleed” due to its automated similarities to the infamous Heartbleed bug, the flaw tracks as CVE-2025-14847 and carries a CVSS score of 7.5.
The vulnerability resides in the MongoDB Server’s zlib message decompression implementation. According to the disclosure released on December 19, 2025, the flaw is an uninitialized memory disclosure issue.
When a MongoDB instance attempts to decompress a specially crafted packet, a logic error allows the requester to read portions of the uninitialized heap memory.
The danger of MongoBleed lies in the data stored in the exposed memory. Because the heap is dynamic, it often contains residue from previous database operations.
Successful exploitation allows an attacker to “bleed” this memory, potentially extracting sensitive artifacts such as cleartext credentials, session tokens, authentication keys, or customer PII that was recently processed by the server.
Critically, this exploit does not require the attacker to be authenticated. Any remote user with network access to the database port can trigger the vulnerability.
The risk is compounded by the fact that zlib compression is enabled by default in standard MongoDB configurations, ensuring a wide attack surface immediately upon disclosure.
According to the internet observability platform Censys, the exposure landscape is significant. As of late December, Censys queries identified over 87,000 potentially vulnerable MongoDB instances exposed to the public internet.
The vulnerability affects a broad range of versions, spanning from legacy deployments to the most recent releases. Affected versions include:
- MongoDB 8.2: 8.2.0 – 8.2.2
- MongoDB 8.0: 8.0.0 – 8.0.16
- MongoDB 7.0: 7.0.0 – 7.0.27
- MongoDB 6.0: 6.0.0 – 6.0.26
- MongoDB 5.0: 5.0.0 – 5.0.31
- MongoDB 4.4: 4.4.0 – 4.4.29
- Legacy: All versions of 4.2, 4.0, and 3.6.
While there is no confirmed evidence of active exploitation in the wild at the time of writing, the window for patching is closing rapidly. A Proof-of-Concept (PoC) exploit has already been published by a researcher, Joe Desimone, on GitHub.
The availability of public exploit code dramatically increases the likelihood that threat actors will begin scanning for and scraping data from unpatched servers.
MongoDB has released patches to address CVE-2025-14847. Administrators are urged to upgrade immediately to the following versions or higher:
- 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32, and 4.4.30.
For organizations unable to apply patches immediately, temporary mitigation strategies are available. Administrators can disable zlib compression by modifying the networkMessageCompressors or net.compression.compressors settings to explicitly omit zlib.
Additionally, restricting network access to trusted IP addresses is a standard best practice for database security that helps prevent remote attackers from reaching vulnerable services.
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