CVE-2018-20802 | Post-auth queries on compound index may crash mongod

A user authorized to perform database queries may trigger denial of service by issuing specially crafted queries with compound indexes affecting QueryPlanner. This issue affects MongoDB Server v3.6 versions prior to 3.6.9 and MongoDB Server v4.0 versions prior to 4.0.3.

Published: 2020-11-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-20802 is rated Moderate Risk (47.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.43%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2018-20802

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-12-28 0.48% 0.43% -0.05%
2 2025-12-27 0.43% 0.48% +0.05%
3 2025-11-21 — 0.43% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-20802

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2018-20802

OS Trackers for CVE-2018-20802

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2018-20802
ubuntu medium CVE-2018-20802 medium priority: Ubuntu including 1 source packages (mongodb), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 11, not-affected 3, released 2. https://ubuntu.com/security/CVE-2018-20802

Affected software / configurations for CVE-2018-20802

Vendor Product Version Raw CPE
mongodb mongodb >= 3.6.0, < 3.6.9 cpe:2.3:a:mongodb:mongodb:*:*:*:*:*:*:*:*
mongodb mongodb >= 4.0.0, < 4.0.3 cpe:2.3:a:mongodb:mongodb:*:*:*:*:*:*:*:*

References for CVE-2018-20802

URL Tags
https://jira.mongodb.org/browse/SERVER-36993 Issue Tracking Vendor Advisory
cvelogic Threat Intelligence