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cve

CVE-2025-14847: MongoBleed Memory Leak Under Active Attack

Security Substrate

— 6 min read

CVE-2025-14847: MongoBleed Memory Leak Under Active Attack

CVE ID: CVE-2025-14847

Severity: HIGH | CVSS: 7.5 (NVD official score)

Sources: 3 different security sources including CISA

Status: Actively exploited in the wild

Let Me Explain What Happened

Sit down for a moment, because this one's important. A serious vulnerability has been discovered in MongoDB—one of the world's most popular database systems—and attackers are already exploiting it in the wild. The flaw, nicknamed "MongoBleed," allows anyone on the internet to read sensitive information directly from a MongoDB server's memory without needing a username or password. Think of it like someone being able to peek through your window and read documents on your desk, even though your front door is locked. What makes this particularly concerning is that CISA added it to their Known Exploited Vulnerabilities catalog on December 29, 2025, confirming that real attacks are happening right now.

A Bit More Detail

Here's what's going on under the hood. MongoDB uses compression to make data transfer more efficient, specifically a technology called Zlib. The problem occurs when the length fields in these compressed protocol headers don't match up properly—imagine a shipping label that says a box contains 10 items, but the actual packing list says 15. When this mismatch happens, MongoDB can accidentally send back chunks of uninitialized heap memory to whoever asked for it. That memory might contain database credentials, application secrets, session tokens, or other sensitive information that was recently processed by the server. The vulnerability has been tracked as CVE-2025-14847 and affects a staggering range of MongoDB versions going back nearly a decade.

The Technical Specifics

  • Attack Vector: NETWORK (remotely exploitable)
  • Attack Complexity: LOW (easy to exploit)
  • Privileges Required: NONE (unauthenticated access)
  • User Interaction: NONE (fully automated attacks possible)
  • CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
  • CWE Classification: CWE-130 (Improper Handling of Length Parameter Inconsistency)
  • Affected Products:
    • MongoDB Server v7.0 prior to 7.0.28
    • MongoDB Server v8.0 prior to 8.0.17
    • MongoDB Server v8.2 prior to 8.2.3
    • MongoDB Server v6.0 prior to 6.0.27
    • MongoDB Server v5.0 prior to 5.0.32
    • MongoDB Server v4.4 prior to 4.4.30
    • MongoDB Server v4.2 (all versions from 4.2.0 onward)
    • MongoDB Server v4.0 (all versions from 4.0.0 onward)
    • MongoDB Server v3.6 (all versions from 3.6.0 onward)
  • Exposure: Over 87,000 potentially vulnerable MongoDB instances identified on the public internet

Note on CVSS Scoring: The NVD lists this vulnerability with a CVSS score of 7.5 (HIGH severity). However, The Hacker News and other sources reported a score of 8.7, likely using a different scoring methodology or considering additional impact factors. For consistency and authority, we're using the official NVD score of 7.5 throughout this analysis.

The Timeline: How This Unfolded

Let me walk you through how this vulnerability came to light, because understanding the timeline helps you appreciate the urgency:

  • December 19, 2025: MongoDB publicly disclosed CVE-2025-14847 in the National Vulnerability Database, providing technical details about the flaw in their Zlib compression handling.
  • December 27, 2025: The Hacker News published the first detailed analysis, explaining how unauthenticated attackers could exploit the vulnerability to read uninitialized heap memory.
  • December 28, 2025: BleepingComputer reported that the vulnerability had been dubbed "MongoBleed" and revealed that over 87,000 potentially vulnerable servers were exposed on the public internet.
  • December 29, 2025: CISA added CVE-2025-14847 to their Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild and mandating remediation for federal agencies.

Why This Matters So Much

You might be wondering why this particular vulnerability has security professionals so concerned. Let me explain. First, the barrier to exploitation is incredibly low—no authentication required, no complex setup needed, just a simple network connection to a vulnerable MongoDB server. Second, the potential impact is severe. Memory leaks can expose database credentials, API keys, encryption keys, session tokens, and other secrets that were recently processed. Third, with 87,000+ exposed instances worldwide, the attack surface is enormous. And finally, CISA's addition to the KEV catalog tells us that attackers aren't just theoretically interested—they're actively scanning for and exploiting vulnerable servers right now.

What You Should Do About This

Here's my guidance, broken down into immediate actions and longer-term protective measures:

  • Right Now (Emergency Response):
    • Identify your MongoDB instances: Create an inventory of all MongoDB servers in your environment, including development, staging, and production systems. Don't forget about containerized deployments or cloud-hosted instances.
    • Check your versions: Compare your MongoDB versions against the affected version list above. If you're running any version prior to the patched releases, you're vulnerable.
    • Assess internet exposure: Determine which MongoDB instances are accessible from the internet. Prioritize these for immediate action, as they're at highest risk.
    • Review access logs: Look for unusual connection patterns, especially repeated connections from unfamiliar IP addresses or connection attempts that don't result in authentication.
    • Consider temporary network isolation: If immediate patching isn't possible, consider temporarily restricting network access to MongoDB servers using firewall rules, allowing only known-good IP addresses.
  • For the Long Term (Remediation):
    • Apply patches immediately: Upgrade to the patched versions: 7.0.28, 8.0.17, 8.2.3, 6.0.27, 5.0.32, or 4.4.30 depending on your version branch. For versions 4.2, 4.0, and 3.6, consider upgrading to a supported version as these older releases may not receive patches.
    • Implement network segmentation: MongoDB servers should never be directly exposed to the internet. Place them behind firewalls and use VPNs or bastion hosts for administrative access.
    • Enable authentication: While this vulnerability can be exploited without authentication, ensuring that authentication is properly configured and enforced adds an important layer of defense.
    • Monitor for exploitation attempts: Set up alerts for unusual connection patterns, failed connection attempts, or unexpected data access patterns.
    • Rotate sensitive credentials: If you suspect a server may have been compromised, rotate all database credentials, API keys, and other secrets that might have been exposed through memory leaks.
    • Review MongoDB security hardening guides: Consult MongoDB's official security checklist and implement recommended hardening measures.

How to Detect Potential Exploitation

If you're running a SIEM or log analysis platform, here are some indicators to watch for:


# Look for connection attempts without subsequent authentication
# (This pattern might indicate exploitation attempts)

# Splunk query example:
index=mongodb sourcetype=mongodb:log
| search "connection accepted" NOT "Successfully authenticated"
| stats count by src_ip
| where count > 10

# Check for unusual connection patterns from single sources
index=mongodb sourcetype=mongodb:log
| stats count by src_ip, dest_port
| where count > 50 AND dest_port=27017

Additionally, monitor your network traffic for:

  • Repeated connections to MongoDB ports (default 27017) from unexpected sources
  • Connection attempts that don't follow normal application patterns
  • Connections from IP addresses associated with scanning or exploitation activity
  • Unusual data transfer volumes from MongoDB servers

Going Deeper: The Technical Mechanics

For those of you who want to understand the vulnerability at a deeper level, let's talk about what's actually happening in the code. MongoDB uses Zlib compression to reduce bandwidth usage when transmitting data between clients and servers. The protocol includes length fields that tell the receiver how much data to expect. The vulnerability (CWE-130: Improper Handling of Length Parameter Inconsistency) occurs when these length fields don't match up correctly.

When a mismatch occurs, MongoDB's memory handling code may read beyond the intended buffer boundaries into uninitialized heap memory. This memory hasn't been cleared since its last use, so it might contain remnants of previous operations—database queries, authentication credentials, session data, or other sensitive information. An attacker can craft malicious requests with intentionally mismatched length fields to trigger this condition and receive chunks of memory in the server's response.

This type of vulnerability is reminiscent of the famous Heartbleed bug (CVE-2014-0160) that affected OpenSSL, which is why the security community has nicknamed it "MongoBleed." Both vulnerabilities involve improper bounds checking that allows attackers to read memory they shouldn't have access to.

MITRE ATT&CK Mapping

For threat intelligence and detection engineering purposes, this vulnerability and its exploitation map to the following MITRE ATT&CK techniques:

  • T1190 - Exploit Public-Facing Application: The primary technique, as attackers exploit a vulnerability in an internet-facing MongoDB server
  • T1552.001 - Unsecured Credentials: Credentials In Files: Memory leaks may expose credentials stored in memory
  • T1078 - Valid Accounts: Credentials obtained through memory leaks could be used for subsequent access
  • T1046 - Network Service Discovery: Attackers must first identify vulnerable MongoDB instances through scanning

A Word of Encouragement

I know this seems overwhelming, especially if you're managing a large MongoDB deployment. But here's the thing: you've got this. The fact that you're reading this analysis means you're taking security seriously, and that's the most important step. Patch management can feel like an endless game of whack-a-mole, but each vulnerability you address makes your environment more resilient. Take it one step at a time—inventory your systems, prioritize based on exposure, and work through the patches systematically. And remember, the security community is here to help. MongoDB has provided clear guidance, patches are available, and you're not alone in dealing with this.

Where I Found This Information

Note: This analysis is based on information from multiple authoritative security sources as of December 29, 2025. The vulnerability is confirmed to be under active exploitation. Always test patches in a non-production environment before deploying to production systems, but given the active exploitation status, prioritize this update highly. If you're running MongoDB versions 4.2, 4.0, or 3.6, strongly consider upgrading to a currently supported version, as these older releases may not receive security updates.

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