MongoBleed: Critical Vulnerability Exposes 80,000+ MongoDB Servers to Data Theft
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A severe vulnerability, dubbed MongoBleed (CVE-2025-14847), is being actively exploited in the wild, potentially exposing the sensitive data of countless organizations. Over 80,000 MongoDB instances are believed to be vulnerable and accessible on the public internet, according to recent reports.
A public exploit and detailed technical information are now available, enabling attackers to remotely extract secrets, credentials, and other confidential data from compromised MongoDB servers. The vulnerability has been assigned a critical severity score of 8.7, and a patch was released on December 19 for self-hosted instances.
How MongoBleed Works: Leaking Secrets Through Compression
The root cause of MongoBleed lies in how the MongoDB Server processes network packets using the zlib library for lossless data compression. Researchers at Ox Security discovered that MongoDB inadvertently returns the amount of allocated memory during message processing, rather than the actual length of the decompressed data.
This flaw allows a threat actor to send a specially crafted, malformed message that claims a larger decompressed size. This triggers the server to allocate a larger memory buffer, inadvertently leaking in-memory data – including sensitive information – to the client.
The leaked data can encompass a wide range of credentials, such as API and cloud keys, session tokens, personally identifiable information (PII), internal logs, configurations, paths, and client-related data. Critically, because decompression occurs before authentication, attackers do not require valid credentials to exploit the vulnerability.
“The PoC exploit code is valid and requires only an IP address of a MongoDB instance to start ferreting out in memory things such as database passwords (which are plain text), AWS secret keys etc.,” noted security researcher Kevin Beaumont.
Widespread Exposure and Active Exploitation
As of December 27, Censys data revealed more than 87,000 potentially vulnerable MongoDB instances exposed on the public internet. The United States hosts the largest concentration of these vulnerable servers, with almost 20,000 instances, followed by China (approximately 17,000) and Germany (nearly 8,000).
The impact extends significantly into cloud environments. Telemetry from cloud security platform Wiz indicates that 42% of visible systems have at least one instance of MongoDB running a version susceptible to CVE-2025-14847. Wiz researchers have confirmed active exploitation of MongoBleed in the wild and strongly recommend immediate patching.
While unconfirmed, some threat actors have reportedly claimed to have leveraged the MongoBleed flaw in a recent breach targeting Ubisoft’s Rainbow Six Siege online platform.
Detection and Mitigation Strategies
Patching remains the primary defense against MongoBleed. MongoDB released updates addressing the vulnerability on December 19, recommending administrators upgrade to one of the following versions: 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32, or 4.4.30.
MongoDB Atlas customers received the patch automatically and do not require any action.
However, patching is not a complete solution. Recon InfoSec co-founder Eric Capuano emphasizes the need to actively search for signs of compromise. Capuano suggests looking for “a source IP with hundreds or thousands of connections but zero metadata events” as a potential indicator of exploitation. He cautions, however, that attackers could modify the proof-of-concept exploit to evade detection.
To aid in detection efforts, Florian Roth, creator of the THOR APT Scanner, developed the MongoBleed Detector, a tool that parses MongoDB logs to identify potential exploitation attempts.
If upgrading is not immediately feasible, MongoDB recommends disabling zlib compression on the server. The vendor also suggests considering alternative lossless data compression tools like Zstandard (zstd) and Snappy, maintained by Meta and Google, respectively.
Affected Versions
MongoDB has warned that a broad range of versions are impacted by MongoBleed (CVE-2025-14847), including legacy releases dating back to late 2017 and versions as recent as November 2025:
- MongoDB 8.2.0 through 8.2.3
- MongoDB 8.0.0 through 8.0.16
- MongoDB 7.0.0 through 7.0.26
- MongoDB 6.0.0 through 6.0.26
- MongoDB 5.0.0 through 5.0.31
- MongoDB 4.4.0 through 4.4.29
- All MongoDB Server v4.2 versions
- All MongoDB Server v4.0 versions
- All MongoDB Server v3.6 versions
Organizations relying on vulnerable MongoDB instances must prioritize patching and actively monitor for signs of compromise to mitigate the risk posed by this critical vulnerability.
