CVE-2026-84965: mongodb c_driver Integer Overflow or Wraparound

Vulnerability summary

CVE-2026-84965 is a medium (CVSS 5.9) Integer Overflow or Wraparound vulnerability in mongodb c_driver. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 1.9% of scored vulnerabilities.

Timeline

1. 03-09-2026
   PublishedVulnerability first disclosed.
2. 03-09-2026
   Last modifiedVulnerability information updated.

Description

An integer wraparound in an allocation size calculation in the BSON library's JSON parsing code can cause a buffer to be released while a following copy operation still writes through the stale pointer. On builds where sizes are 32 bits, an unauthenticated party able to supply a sufficiently large JSON input to an application that links the library may cause that application to terminate unexpectedly, resulting in denial of service.

• CWE-190Integer Overflow or WraparoundThe product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.