{"affected":[{"defaultStatus":"unaffected","product":"C# Driver","source":"CNA: mongodb","vendor":"MongoDB","versions":[{"lessThan":"3.14.0","status":"affected","version":"2.21.0","versionType":"semver"}]}],"cveId":"CVE-2026-126839","cwes":["CWE-502"],"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.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":2.3,"severity":"low","source":"CNA: mongodb","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","version":"4.0"},{"score":4.2,"severity":"medium","source":"CNA: mongodb","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L","version":"3.1"}],"modifiedAt":1794527896490,"publishedAt":1794527896490,"references":[{"source":"CNA: mongodb","tags":[],"url":"https://jira.mongodb.org/browse/CSHARP-6169"}],"remediation":[],"revision":"4c8dba77a04e6bb8d171c4b7d3587318a07fea35de2d6abdf180edb8c91806bd","sources":[{"modifiedAt":1794527896490,"name":"CNA: mongodb","retrievedAt":1794528549405,"url":"https://www.cve.org/CVERecord?id=CVE-2026-126839"}],"ssvc":null,"status":"published","title":"Deserialization allow-list bypass via anonymous-type misdetection in BSON object deserialization","updatedAt":1794528549405}