Summary
A critical unauthenticated vulnerability dubbed MongoBleed (CVE-2025-14847) has been disclosed in MongoDB’s zlib message compression, allowing remote attackers to extract sensitive data from uninitialized memory. This flaw affects nearly all versions released since 2017, enabling the exfiltration of credentials, PII, and session tokens without requiring authentication. While MongoDB released patches for supported versions in late December 2025, End-of-Life versions such as 3.6, 4.0, and 4.2 remain permanently vulnerable. With over 87,000 internet-exposed instances identified, RH-ISAC Core Members are encouraged to review the intelligence in this report.
Sector Impact
Retail and hospitality sectors processing high volumes of customer PII and loyalty data remain particularly susceptible, as a successful exploit yields immediate access to sensitive records without triggering standard authentication alarms. Organizations utilizing legacy inventory or booking systems built on older, unpatched MongoDB instances face elevated risks of massive data breaches and regulatory penalties. As such, RH-ISAC Core Members should review the intelligence in this alert and the recommended mitigations against MongoBleed, included below.
Analysis
The vulnerability creates a memory exposure risk by exploiting how MongoDB handles zlib-compressed payloads. An attacker triggers the flaw by declaring a large uncompressed packet size while sending a small payload, causing the server to allocate memory that retains residual data from previous operations. Because the server fails to verify the actual uncompressed length, it processes uninitialized heap memory containing secrets like API keys and cleartext credentials. Malicious actors then force the server to parse this memory as BSON fields, triggering error messages that return the sensitive data directly to the attacker.
Mitigation
According to Abstract Security, organizations using MongoDB should take immediate action to patch this critical vulnerability.
Immediate Actions:
- Upgrade MongoDB to patched versions referenced in the Patched Versions section.
- Enable command error logging to be able to detect suspicious and malicious MongoDB queries.
Risk Assessment:
- Identify all MongoDB deployments and ensure they have proper logging and network IDS visibility enabled.
- Review network segmentation to determine if MongoDB instances can be segmented further.
Immediate Workarounds (if patching is not immediately feasible):
- Disable ZLIB compression support from within MongoDB until a patch can be applied.
Detection and Monitoring:
- Enable comprehensive logging for all document processing workflows, including full request payloads where feasible.
- Implement real-time monitoring for large spikes (>1k “Slow query” logs) in errors caused on the MongoDB systems.
- Correlate “Slow query” logs with upstream network traffic to ensure rapid mitigation for ongoing attacks.
