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.
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Fixes
Solution
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Workaround
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References
| Link | Providers |
|---|---|
| https://jira.mongodb.org/browse/CSHARP-6169 |
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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 |
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| Metrics |
cvssV3_1
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Projects
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Status: PUBLISHED
Assigner: mongodb
Published:
Updated: 2026-11-12T23:58:16.490Z
Reserved: 2026-11-11T22:04:48.453Z
Link: CVE-2026-126839
No data.
Status : Received
Published: 2026-11-13T00:20:13.080
Modified: 2026-11-13T00:20:13.080
Link: CVE-2026-126839
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OpenCVE Enrichment
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Weaknesses