# CVE-2026-120809: Heap use-after-free read via yield-time state save in time-series block unpacking

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

A use-after-free read issue exists in MongoDB’s SBE (Slot-Based Execution) engine when processing aggregation pipelines with $unwind on time-series collections. An internal error in state-preservation logic can cause a value still referenced by downstream stages to have its underlying memory freed prematurely. An authenticated user can craft an aggregation pipeline under specific conditions to trigger this condition, potentially reading recycled server heap memory in query results or crashing the server. This issue is only triggerable when a non-default server parameter related to the SBE engine is enabled.

## 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). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 6.1 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 6.8 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H; source: CNA: mongodb

- CVSS 4.0: 6.1 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:H/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: 6.8 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H; source: NVD: cna@mongodb.com

- CISA KEV: No listing in collected sources

- EPSS: 0.37% as of 2026-11-13; percentile 31.19%

- 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-132279 (CNA: mongodb)

- https://jira.mongodb.org/browse/SERVER-132279 (cna@mongodb.com)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-120809; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-120809; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-120809; retrieved 2026-11-13; source updated Not reported

Revision: efac93cbe911a4ff04216c3341ea02c312271d056ee867b991b4df71042cd83f

Canonical: https://y2.dev/cve/CVE-2026-120809

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