EUVD-2026-47778Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Sharded topology with Atlas Search and per-user ACLs required (AC:H); valid authenticated account mandatory (PR:L); confidentiality-only impact, no scope change.
Primary rating from Vendor (mongodb).
CVSS VectorVendor: mongodb
Lifecycle Timeline
2DescriptionCVE.org
An issue in the server’s Atlas Search integration allows an authenticated user to bypass per-user access controls.
In sharded topologies, the $search and $searchMeta aggregation stages use internal routing that is normally populated only by the trusted router during sharded search planning. Due to insufficient input validation, an authenticated client can supply these fields directly.
AnalysisAI
Atlas Search integration in MongoDB's sharded topology exposes a per-user access control bypass to authenticated low-privileged users. The $search and $searchMeta aggregation pipeline stages rely on internal routing fields that are intended to be injected exclusively by the trusted mongos router during sharded query planning; due to insufficient input validation (CWE-20), an authenticated client can supply these fields directly and circumvent the access controls normally enforced per-user. No public exploit has been identified at time of analysis, and the vulnerability is not listed in CISA KEV; the CVSS 4.0 score of 6.0 reflects the combination of high confidentiality impact against a sharded-only attack surface requiring authenticated access.
Technical ContextAI
The vulnerability resides in the server-side handling of MongoDB's Atlas Search aggregation stages ($search and $searchMeta) within sharded cluster topologies. In a sharded deployment, the mongos router normally enriches these pipeline stages with internal routing metadata - fields that direct search queries to the correct shard(s) during planning. Because the underlying aggregation stage handler performs insufficient input validation (CWE-20: Improper Input Validation), it does not distinguish between routing context legitimately injected by the trusted router and context injected directly by a client. This breaks the trust boundary that Atlas Search relies upon to enforce per-user access control policies, allowing an authenticated user to craft a pipeline that presents routing context outside their privilege boundary. The flaw is specific to the Atlas Search integration layer - not the core aggregation engine - and only manifests in sharded topologies where this routing handshake is exercised.
RemediationAI
Apply the patch referenced in MongoDB Jira ticket SERVER-126247 (https://jira.mongodb.org/browse/SERVER-126247); the exact fixed MongoDB server version is not independently confirmed from available data and must be verified directly against the MongoDB advisory or release notes. As a compensating control pending patching, restrict aggregation pipeline execution privileges - particularly $search and $searchMeta stages - to only trusted, high-privilege accounts in sharded environments, reducing the pool of principals who could abuse the injection vector. Additionally, audit recent aggregation pipeline activity in sharded clusters for unexpected cross-boundary $search usage that may indicate exploitation. Organizations not running sharded topologies or not using Atlas Search require no action. Note that restricting pipeline access may impact legitimate Atlas Search workloads and should be tested before deployment.
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Same weakness CWE-20 – Improper Input Validation
View allSame technique Authentication Bypass
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External POC / Exploit Code
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