# CVE-2026-4148: ExpressionContext use-after-free in classic engine $lookup and $graphLookup aggregation operators

CVE-2026-4148 is fixed in MongoDB on 1 platform by MongoDB 8.2.6 (version 8.2.6), released February 25, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-4148
- Priority: High
- CVSS: 8.7
- EPSS: 0.0034
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 17, 2026
- Weakness: CWE-416: Use after free
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-4148

## Description

A use-after-free vulnerability can be triggered in sharded clusters by an authenticated user with the read role who issues a specially crafted $lookup or $graphLookup aggregation pipeline.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | MongoDB | 8.2.6 | [MongoDB 8.2.6](https://patchblox.com/security/data/fix/windows-app/mongodb.server-8.2.6.md) | Feb 25, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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