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Severe, 6 weeks1498Projects326

1498 severe, 6 weeks · 326 projects

MongoDBGHSA-8vwp-6h6c-hx6h

Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser

MongoDB

CVE-2026-84963 · Published Sep 3, 2026

Medium6.3
Fix: upgrade to 1.30.9 or later (2 fixed versions below)
GitHub advisory

Impact

An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause an unusually large text value to be silently shortened, or the corresponding field to be omitted, while the parsing operation still reports success and returns no error. An unauthenticated party who can supply the input processed by an application that uses this component may cause that application to hold data that does not match what was submitted, which may result in unintended alteration of data.

Patches

Fixed in 1.30.9 and 2.5.2

Workarounds

Validate length of inputs before processing JSON.

References

https://jira.mongodb.org/browse/CDRIVER-6407

Affected versions

PackageAffectedFixed in
MongoDB C Driver
Product
>= 1.10.0, < 1.30.91.30.9
>= 2.0.0, < 2.5.22.5.2
Details and references
CVSS 4.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Severity from
GitHub (reviewed advisory)

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