New MongoDB Flaw Lets Unauthenticated Attackers Read Uninitialized Memory

A high-severity security flaw has been disclosed in MongoDB that could allow unauthenticated users to read uninitialized heap memory.

The vulnerability, tracked as CVE-2025-14847 (CVSS score: 8.7), has been described as a case of improper handling of length parameter inconsistency, which arises when a program fails to appropriately tackle scenarios where a length field is inconsistent with the actual length of the associated data.

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“Mismatched length fields in Zlib compressed protocol headers may allow a read of uninitialized heap memory by an unauthenticated client,” according to a description of the flaw in CVE.org.

The flaw impacts the following versions of the database –

• 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

The issue has been addressed in MongoDB versions 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32, and 4.4.30.

“An client-side exploit of the Server’s zlib implementation can return uninitialized heap memory without authenticating to the server,” MongoDB said. “We strongly recommend upgrading to a fixed version as soon as possible.”

If immediate update is not an option, it’s recommended to disable zlib compression on the MongoDB Server by starting mongod or mongos with a networkMessageCompressors or a net.compression.compressors option that explicitly omits zlib. The other compressor options supported by MongoDB are snappy and zstd.

“CVE-2025-14847 allows a remote, unauthenticated attacker to trigger a condition in which the MongoDB server may return uninitialized memory from its heap,” OP Innovate said. “This could result in the disclosure of sensitive in-memory data, including internal state information, pointers, or other data that may assist an attacker in further exploitation.”

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