This vulnerability is triggered when an aggregation pipeline uses the internal $exchange stage configured with key‑range partitioning and order‑preserving delivery. If a single key range produces enough documents to fill its exchange buffer, the server enters a code path where a full per‑consumer buffer is detected but the internal high watermark for that key range is not updated as intended. The result is a fatal error that causes the MongoDB Server to crash. The flaw is classified as CWE‑617 and results in a Denial of Service, removing availability of the database for any sessions connected to the affected instance.

The affected product is MongoDB Server. The CVE does not specify version numbers, so any MongoDB Server release that has not yet addressed SERVER‑124031 may be vulnerable. Users should verify if their deployed version is affected.

The CVSS base score of 7.1 indicates a moderate‑to‑high severity. No EPSS value is available, so the exact exploitation probability is unknown. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is any aggregation query executed by an application or user that can specify a $exchange stage with key‑range partitioning. As such, an attacker who can construct such a query could trigger a crash, leading to a denial of service for all clients.