# CVE-2026-120811: Use-After-Free in MongoDB Server Classic Query Engine Plan Cache Leads to Information Disclosure and Denial of Service

Status: published. Published: 2026-11-10. Updated: 2026-11-13.

A use-after-free issue exists in the MongoDB server’s classic query engine plan cache. Under certain query conditions, an unowned reference to data from an earlier command can be retained in cached plan statistics. After the originating memory is freed, a subsequent diagnostic command serializing those statistics can read freed heap memory, potentially returning sensitive server process memory contents to the authenticated client. Under certain heap reuse conditions, this may also cause the server to crash.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- MongoDB / MongoDB Server: ≥ 9.0.0; < 9.0.7 (affected, semver); ≥ 8.3.0; < 8.3.16 (affected, semver); ≥ 8.0.0; < 8.0.37 (affected, semver); ≥ 7.0.0; < 7.0.48 (affected, semver). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:L; source: CNA: mongodb

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:L/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; source: NVD: cna@mongodb.com

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:L; source: NVD: cna@mongodb.com

- CISA KEV: No listing in collected sources

- EPSS: 0.26% as of 2026-11-13; percentile 18.32%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-416

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://jira.mongodb.org/browse/SERVER-135353 (CNA: mongodb)

- https://jira.mongodb.org/browse/SERVER-135353 (cna@mongodb.com)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-120811; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-120811; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-120811; retrieved 2026-11-13; source updated Not reported

Revision: 1ca440e662289f9e858d028e0042d5dff45d259e874b07c7b667da813d3de8d9

Canonical: https://y2.dev/cve/CVE-2026-120811

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