# CVE-2026-126982: Remote code execution via generic-type allow-list bypass in BSON object deserialization

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

A type allow-list bypass in the BSON serialization library of the MongoDB C# Driver allows a type-restriction check to be circumvented when polymorphic data is deserialized into loosely typed members. An unauthorized party who can supply or plant BSON/JSON data that the application later deserializes can cause the application process to instantiate .NET types outside the intended allow-list and populate them with unauthorized party-controlled values. In applications that contain a suitable gadget type, this can lead to arbitrary code execution in the context of the application, with corresponding loss of confidentiality, integrity, and availability. No special privileges beyond the ability to introduce data the application reads are required.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- MongoDB / C# Driver: ≥ 3.2.0; < 3.14.0 (affected, semver). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 7.7 (high); CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: mongodb

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-502

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://jira.mongodb.org/browse/CSHARP-6160 (CNA: mongodb)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-126982; retrieved 2026-11-13; source updated 2026-11-13

Revision: 5ec66cf96c1d85827d2aabbec77b491f42bd03ea1cd10e932533487f671db105

Canonical: https://y2.dev/cve/CVE-2026-126982

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.