Description
A deserialization type-restriction control in the BSON serialization component can be bypassed because the check used to recognize a class of compiler-generated types relies on an overly permissive heuristic rather than a precise identification. An unauthorized party able to supply BSON content that an application later deserializes into a loosely typed member can cause types outside the intended allow-list to be constructed and populated with unauthorized party-supplied values inside the consuming application. This can lead to unexpected object state and errors in downstream application logic. No elevated privileges beyond the ability to place unauthorized party-influenced content in the deserialization path are required.
Published: 2026-11-12
Score: 2.3 Low
EPSS: < 1% Very Low
KEV: No
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Remediation

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History

Fri, 13 Nov 2026 00:30:00 +0000

Type Values Removed Values Added
Description A deserialization type-restriction control in the BSON serialization component can be bypassed because the check used to recognize a class of compiler-generated types relies on an overly permissive heuristic rather than a precise identification. An unauthorized party able to supply BSON content that an application later deserializes into a loosely typed member can cause types outside the intended allow-list to be constructed and populated with unauthorized party-supplied values inside the consuming application. This can lead to unexpected object state and errors in downstream application logic. No elevated privileges beyond the ability to place unauthorized party-influenced content in the deserialization path are required.
Title Deserialization allow-list bypass via anonymous-type misdetection in BSON object deserialization
Weaknesses CWE-502
References
Metrics cvssV3_1

{'score': 4.2, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L'}

cvssV4_0

{'score': 2.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: mongodb

Published:

Updated: 2026-11-12T23:58:16.490Z

Reserved: 2026-11-11T22:04:48.453Z

Link: CVE-2026-126839

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-13T00:20:13.080

Modified: 2026-11-13T00:20:13.080

Link: CVE-2026-126839

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-502

    Deserialization of Untrusted Data