No exploitation reported

CVE-2021-31372

No exploitation reported by the sources we read.

Published2021-10-19
WeaknessCWE-20

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

An Improper Input Validation vulnerability in J-Web of Juniper Networks Junos OS allows a locally authenticated J-Web attacker to escalate their privileges to root over the target device. This issue affects: Juniper Networks Junos OS All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2, 21.1R3; 21.2 versions prior to 21.2R1-S1, 21.2R2;

Timeline

dates in UTC

2021-10-1919:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-31372?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-31372?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Juniper junos

Branch	Affected	Fixed in	Source
18.2	≤ 18.2	no fix published	NVD
18.3	= 18.3	no fix published	NVD
18.4	= 18.4	no fix published	NVD
19.1	= 19.1	no fix published	NVD
19.2	= 19.2	no fix published	NVD
19.3	= 19.3	no fix published	NVD
19.4	= 19.4	no fix published	NVD
20.1	= 20.1	no fix published	NVD
20.2	= 20.2	no fix published	NVD
20.3	= 20.3	no fix published	NVD
20.4	= 20.4	no fix published	NVD
21.1	= 21.1	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

kb.juniper.netVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.18.8read 2026-10-23
NVDCVSS 2.09read 2026-10-23
CNAweakness (CWE)CWE-20read 2026-10-23
NVDweakness (CWE)CWE-20read 2026-10-23
FIRST EPSSEPSS score1.2 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published: 2021-10-19
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-31372?

Is CVE-2021-31372 actively exploited?

Active exploitation of CVE-2021-31372 has not been confirmed. Its EPSS score was 1.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-31372?

CVE-2021-31372 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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