CVE-2018-20803

Infinite loop in aggregation expression

6.5 Medium

A user authorized to perform database queries may trigger denial of service by issuing specially crafted queries, which loop indefinitely in mathematics processing while retaining locks. This issue affects MongoDB Server v4.0 versions prior to 4.0.5; MongoDB Server v3.6 versions prior to 3.6.10 and MongoDB Server v3.4 versions prior to 3.4.19.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

1.44%Up 0.9 points since Apr 14, 2021

What each source reports

CVE List Score used 6.5

Infinite loop in aggregation expression

Record: CVE-2018-20803
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-835
Updated: 2026-11-02

EUVDEUVD-2018-13345 6.5

Record: EUVD-2018-13345
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-03

GitHub AdvisoriesGHSA-w7g3-8fq6-h7f2 6.5

A user authorized to perform database queries may trigger denial of service by issuing specially...

A user authorized to perform database queries may trigger denial of service by issuing specially crafted queries, which loop indefinitely in mathematics processing while retaining locks. This issue affects: MongoDB Inc. MongoDB Server v4.0 versions prior to 4.0.5; v3.6 versions prior to 3.6.10; v3.4 versions prior to 3.4.19.

Record: GHSA-w7g3-8fq6-h7f2
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-835
Updated: 2026-11-02

NVD 6.5

Record: CVE-2018-20803
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 4.0 MediumAV:N/AC:L/Au:S/C:N/I:N/A:P
Weakness: CWE-835
Updated: 2026-11-02

OSV 6.5

Record: CVE-2018-20803
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2018-20803 6.5

Record: UBUNTU-CVE-2018-20803
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mongodb` Ubuntu:Pro:14.04:LTS	All versions, plus listed versions 1:2.4.6-0ubuntu51:2.4.6-0ubuntu61:2.4.8-1ubuntu11:2.4.8-21:2.4.9-11:2.4.9-1ubuntu11:2.4.9-1ubuntu21:2.4.9-1ubuntu2+esm2	None known
`mongodb` Ubuntu:Pro:16.04:LTS	All versions, plus listed versions 1:2.6.10-0ubuntu11:2.6.10-0ubuntu1+esm2	None known
`mongodb` Ubuntu:Pro:18.04:LTS	All versions, plus listed versions 1:3.4.7-11:3.4.7-1ubuntu11:3.4.7-1ubuntu21:3.4.7-1ubuntu41:3.4.14-3ubuntu1 Show 7 moreShow less 1:3.4.14-3ubuntu21:3.6.3-0ubuntu11:3.6.3-0ubuntu1.11:3.6.3-0ubuntu1.31:3.6.3-0ubuntu1.41:3.6.3-0ubuntu1.4+esm11:3.6.3-0ubuntu1.4+esm2	None known
`mongodb` Ubuntu:Pro:20.04:LTS	All versions, plus listed versions 1:3.6.9+really3.6.8+90~g8e540c0b6d-0ubuntu21:3.6.9+really3.6.8+90~g8e540c0b6d-0ubuntu51:3.6.9+really3.6.8+90~g8e540c0b6d-0ubuntu5.21:3.6.9+really3.6.8+90~g8e540c0b6d-0ubuntu5.31:3.6.9+really3.6.8+90~g8e540c0b6d-0ubuntu5.3+esm1	None known

History

History
Recorded	Changed	Sources
Nov 10, 2026	facts
Nov 3, 2026	aliases, products, published	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2018-20803 is a medium vulnerability (CVSS 6.5) in Mongodb, published November 23, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.44%, the 73rd percentile. No source names a fixed version.