CVE-2026-82071: 
MongoDB Analisi e mitigazione delle vulnerabilità

CVE-2026-82071 is an out-of-bounds write vulnerability in MongoDB Server caused by insufficient validation of storage engine configuration options. An authenticated user with write privileges can supply crafted parameters during collection creation that override internal storage metadata, triggering an out-of-bounds memory write. This can result in a denial of service via server crash, with potential for arbitrary code execution. Affected versions are MongoDB Server 8.3.0 through 8.3.8 (fixed in 8.3.9). The vulnerability carries a CVSS v3.1 base score of 8.1 (High) and a CVSS v4.0 base score of 7.2 (High) (Feedly, EUVD).

The root cause is classified as CWE-787 (Out-of-bounds Write), stemming from insufficient validation of storage engine configuration parameters passed during collection creation. An attacker with network access and low-privilege write credentials can craft malicious parameters that override internal storage metadata, causing the server process to write memory outside its allocated buffer. The attack requires no user interaction and has low attack complexity, making it straightforward to exploit once valid credentials are obtained. The vulnerability is tracked upstream in MongoDB's issue tracker as SERVER-131860 (EUVD, MongoDB JIRA).

Successful exploitation causes an out-of-bounds memory write in the MongoDB server process, leading to a server crash and denial of service. Beyond availability, the vulnerability carries high integrity impact, as crafted parameters can corrupt internal storage metadata. There is also potential for arbitrary code execution, which could allow an attacker to escalate from a low-privilege database account to full server compromise, enabling data exfiltration or lateral movement within the environment (Feedly).

As of the disclosure date (September 8, 2026), there are no known public proof-of-concept exploits, no reported in-the-wild exploitation, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS score is 0.0, reflecting low current exploitation probability. The NVD SSVC assessment classifies exploitation as "none" and technical impact as "partial" (Feedly, EUVD).

1. Reconnaissance: Identify MongoDB Server instances running versions 8.3.0–8.3.8 exposed on the network (default port 27017). Tools such as Shodan or Censys can be used to locate internet-facing instances.
2. Obtain credentials: Acquire valid MongoDB credentials with write privileges to at least one database. This could be achieved through credential stuffing, phishing, or exploitation of misconfigured authentication.
3. Connect to the server: Establish a connection to the target MongoDB instance using the mongo shell or a compatible driver with the obtained credentials.
4. Craft malicious collection creation request: Issue a db.createCollection() command with specially crafted storage engine configuration options designed to override internal storage metadata (e.g., manipulated storageEngine parameters in the options document).
5. Trigger out-of-bounds write: The server processes the malformed parameters without sufficient validation, causing an out-of-bounds memory write that crashes the server process (DoS) or, under favorable memory layout conditions, may enable arbitrary code execution (Feedly, MongoDB JIRA).

• Network: Unexpected or repeated connections to MongoDB port (27017/TCP) from unusual source IPs; authenticated sessions issuing createCollection commands with non-standard storageEngine parameters.
• Logs: MongoDB server logs (mongod.log) showing abrupt process termination or segmentation fault entries; log entries referencing collection creation with unusual or malformed storage engine options.
• Process: Unexpected crash or restart of the mongod process; core dump files generated in the MongoDB working directory following a crash.
• File System: Presence of core dump files (e.g., core, core.mongod.*) in the MongoDB data or working directory, indicating an abnormal process termination (Feedly).

MongoDB has released version 8.3.9 to address this vulnerability; administrators should upgrade all affected MongoDB Server instances from the 8.3.x branch to 8.3.9 or later as the primary remediation. As a temporary workaround, restrict write access to trusted users only and limit network exposure of MongoDB instances using firewall rules or network segmentation to reduce the attack surface. Monitoring for unusual createCollection commands with non-standard storage engine parameters can help detect exploitation attempts (EUVD, MongoDB JIRA).