# CVE-2026-120678: mongo-c-driver leaks the decompressed reply buffer when an OP_COMPRESSED reply fails to parse (denial of service)

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

A memory management flaw in the MongoDB C Driver's handling of compressed responses may cause the client library to hold on to memory that is never released. An unauthenticated party that controls the database endpoint a client application connects to may cause repeated, unbounded memory growth in that application, which may result in the application becoming unavailable. No credentials, transport security settings, or user interaction are required.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- MongoDB / C Driver: ≥ 1.25.0; ≤ 1.30.14 (affected, semver); ≥ 2.0.0; ≤ 2.5.7 (affected, semver). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: mongodb

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-401

## Exploit evidence

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

## References

- https://jira.mongodb.org/browse/CDRIVER-6521 (CNA: mongodb)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-120678; retrieved 2026-11-03; source updated 2026-11-03

Revision: 5af55c6bc2d322dfbfb40c620c77adecfffd51ca62e0194aa5cfcfdff0bea283

Canonical: https://y2.dev/cve/CVE-2026-120678

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