MongoDB Server EUVD-2026-47789

Exploitation requires that the target be a standalone mongod instance started with compute mode explicitly enabled - this is a non-default startup configuration and is the single most important limiting factor; default MongoDB deployments are not affected. The attacker must be able to send an aggregation pipeline request carrying attacker-controlled BSON to the server over the network (AV:N, PR:N, UI:N per the vendor vector), and must craft that BSON to trigger the heap overflow, which the vendor rates as high complexity (AC:H) with a present attack requirement (AT:P). Limiting factors: the non-default compute mode requirement, high crafting complexity, and network reachability of the mongod port; note also that submitting aggregation queries may in many real deployments require database authentication even though the CVSS vector lists PR:N, so authentication requirements should be verified against the vendor advisory.

The signals are mixed and should be weighed carefully rather than taken at CVSS face value. The vendor CVSS 4.0 base score is 9.2 (Critical) with AV:N/PR:N/UI:N (network-reachable, no privileges, no user interaction) and VC:H/VI:H/VA:H, but two metrics temper this materially: AC:H (high attack complexity) and AT:P (a present attack requirement), the latter reflecting that the vulnerable compute mode is non-default and must be explicitly enabled. In practice the confirmed, described impact is memory corruption leading to 'process termination or other unintended behavior' - i.e. a reliable denial of service - while the H confidentiality/integrity ratings appear to reflect the theoretical worst case of heap corruption rather than a demonstrated code-execution or data-disclosure primitive; this is a notable point of tension between the vector and the description. No EPSS score, KEV entry, or POC was provided, so exploitation probability cannot be quantified and there is no evidence of in-the-wild use. Real-world priority is therefore driven almost entirely by whether an organization actually runs standalone mongod in compute mode: for the vast majority of default deployments this is not exploitable, making it a conditional/targeted concern rather than a broad emergency.

An attacker able to reach a standalone mongod running in compute mode submits an aggregation query containing crafted BSON with malformed size/length structure; during pipeline processing the server writes past a heap buffer, corrupting memory and crashing the mongod process, causing a denial of service for all dependent applications. Because attack complexity is high (AC:H) and the vulnerable compute mode must already be enabled (AT:P), reliable exploitation requires both the specific server configuration and a carefully constructed payload; no public exploit code has been identified at time of analysis.