As previously reported, a serious vulnerability has been discovered in MongoDB that allows a remote attacker, without authentication, to access uninitialized server memory. The vulnerability has been assigned the CVE-2025-14847 identifier and a CVSS score of 8.7, representing a high severity level.
The CWE-130 error is related to incorrect processing of data length parameters. In some situations, the server does not correctly match the length value specified in the header to the actual amount of data transferred.
This is due to the Zlib compression data exchange protocol : if the length fields in the compressed header do not match the actual content, MongoDB may return a previously uninitialized memory location to the client.
Simply put, a specially crafted request allows fragments of a server’s RAM to be read without logging in. This data may contain the process’s internal state, pointers, service structures, or other information that facilitates further attacks.
The vulnerability affects a wide range of MongoDB Server versions:
Developers have already released updates that address the issue. The fixes are available in versions 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32, and 4.4.30. MongoDB emphasizes that the vulnerability can be exploited client-side and does not require credentials, so it’s recommended to install the update as soon as possible.
MongoBleed runs before authentication checks. By crafting malformed and compressed network packets, unauthenticated attackers can now trick the server into mishandling the lengths of decompressed messages, resulting in the server returning uninitialized heap memory fragments directly to the client.
The root cause lies in message_compressor_zlib.cpp, where the vulnerable code returned the size of the allocated buffer rather than the actual length of the decompressed data. This subtle but critical flaw allows undersized or malformed payloads to expose adjacent heap memory containing sensitive information, a buffer overflow vulnerability similar to Heartbleed.
Because the flaw is reachable before authentication and requires no user interaction, Internet-facing MongoDB servers are at immediate risk of exploitation.
According to Censys , there are currently approximately 87,000 potentially vulnerable instances exposed worldwide, while Wiz research indicates that 4.2% of cloud environments host at least one vulnerable MongoDB instance.
In the last few days, several repositories dedicated to the exploitation and detection of CVE-2025-14847 , a critical memory disclosure vulnerability in MongoDB related to the management of zlib compression ( OP_COMPRESSED flag), have been published on GitHub.
Projects such as ProbiusOfficial/CVE-2025-14847 and cybertechajju/CVE-2025-14847_Exploit provide proof-of-concept and working exploits demonstrating how sensitive data can be extracted directly from the heap of vulnerable MongoDB instances, highlighting the real-world impact of the bug.
Alongside exploits, detection and scanning tools have also appeared, such as onewinner/CVE-2025-14847 and Black1hp/mongobleed-scanner , designed to quickly identify exposed systems, very useful in bug bounty, red teaming and security assessment contexts.
The Ashwesker/Blackash-CVE-2025-14847 repository completes the picture by offering another implementation focused on vulnerability analysis.
Overall, this wave of tools confirms the community’s high level of attention to the flaw and its real danger in production scenarios , especially for MongoDB databases exposed to the network or not adequately updated.
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