Vulnerability · Published Oct 22, 2026 · Assigned by mongodb
CVE-2026-114654BSON output corruption via out-of-range binary subtype bypassing UUID and OldBinary guards
Medium 6.5
In plain English
A medium-severity security flaw in C# Driver from MongoDB. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 29% of all known vulnerabilities).
Official description
A numeric-type conversion flaw in the BSON handling library of the MongoDB C# Driver allows an out-of-range binary subtype value supplied through untrusted textual input to bypass the library's binary-element integrity checks. When such a value is later encoded, it is narrowed to a smaller wire representation, producing binary elements that misdeclare their type or length. An unauthenticated party able to supply text parsed by an affected application can cause it to emit and persist malformed binary data, which subsequent readers either reject with an error or silently interpret as shorter than the data that was validated.
Affected products (as reported)
Weakness: CWE-681 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L