A proof-of-concept (PoC) exploit dubbed “mongobleed” for CVE-2025-14847, a critical unauthenticated memory leak vulnerability in MongoDB’s zlib decompression handling.
Dubbed by its creator Joe Desimone as a way to bleed sensitive server memory, the flaw lets attackers remotely extract uninitialized data without credentials, potentially exposing internal logs, system stats, and more.
The vulnerability stems from a flaw in MongoDB’s processing of compressed messages. Attackers send a specially crafted message claiming an inflated “uncompressedSize.” MongoDB allocates a large buffer based on this claim, but zlib only decompresses the actual data into the …
A proof-of-concept (PoC) exploit dubbed “mongobleed” for CVE-2025-14847, a critical unauthenticated memory leak vulnerability in MongoDB’s zlib decompression handling.
Dubbed by its creator Joe Desimone as a way to bleed sensitive server memory, the flaw lets attackers remotely extract uninitialized data without credentials, potentially exposing internal logs, system stats, and more.
The vulnerability stems from a flaw in MongoDB’s processing of compressed messages. Attackers send a specially crafted message claiming an inflated “uncompressedSize.” MongoDB allocates a large buffer based on this claim, but zlib only decompresses the actual data into the buffer’s start.
Crucially, the server treats the entire buffer as valid, leading BSON parsing to interpret uninitialized memory as field names until it encounters null bytes. By probing different offsets, attackers can systematically leak chunks of memory.
“Mongobleed systematically scans memory regions by crafting malformed BSON documents with varying length fields,” Desimone explained in the GitHub repo. Each probe reveals fragments like MongoDB WiredTiger configs, /proc/meminfo stats, Docker paths, connection UUIDs, and client IPs.
Affected versions span multiple branches:
| Version Branch | Affected Range | Fixed In |
|---|---|---|
| 8.2.x | 8.2.0 – 8.2.2 | 8.2.3 |
| 8.0.x | 8.0.0 – 8.0.16 | 8.0.17 |
| 7.0.x | 7.0.0 – 7.0.27 | 7.0.28 |
| 6.0.x | 6.0.0 – 6.0.26 | 6.0.27 |
| 5.0.x | 5.0.0 – 5.0.31 | 5.0.32 |
The Python-based tool is straightforward to deploy. Basic usage scans offsets 20-8192: python3 mongobleed.py –host <target>. Deeper scans extend to 50,000 offsets for richer leaks, dumping data to a binary file.
Example output reveals system metrics like “MemAvailable: 8554792 kB” and network stats such as “SyncookiesFailed EmbryonicRsts.”
Desimone included a Docker Compose setup for testing vulnerable instances, underscoring the ease of reproduction. Leaked data in demos totaled over 8,700 bytes across 42 fragments.
MongoDB patched the issue in upstream commits, validating decompressed lengths before buffer processing. OX Security first disclosed the flaw, warning of exfiltration risks in cloud and containerized deployments.
Organizations running exposed MongoDB instances, common in web apps, analytics, and NoSQL stacks, face urgent patch pressure. Disable unauthenticated access and monitor for anomalous scans on port 27017.
Desimone, known on X as @dez_ _, released the repo to hasten awareness. As memory leaks like this proliferate, it highlights decompression bugs as a rising vector in database security.
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