Is CVE-2021-31355 being actively exploited?

CVE-2021-31355 is not currently listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

What is the CVSS score for CVE-2021-31355?

CVE-2021-31355 has a CVSS 3.1 base score of 8.0 (HIGH).

CVE-2021-31355

HIGH · CVSS 8.0EPSS 0.8%EU EUVD

A persistent cross-site scripting (XSS) vulnerability in the captive portal graphical user interface of Juniper Networks Junos OS may allow a remote authenticated user to inject web script or HTML and steal sensitive data and credentials from a web administration session, possibly tricking a follow-on administrative user to perform administrative actions on the device. This issue affects Juniper Networks Junos OS: All versions, including the following supported releases: 12.3X48 versions prior to 12.3X48-D105; 15.1X49 versions prior to 15.1X49-D220; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S7; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R3-S4; 19.4 versions prior to 19.4R3-S6; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R1-S1, 20.2R2; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2; 21.1 versions prior to 21.1R2.

Key facts

CVSS score: 8.0 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-79
EPSS score: 0.8% (56th percentile)
In CISA KEV: No
In EU EUVD: Yes (EUVD-2021-18265)
Published: October 19, 2021
NVD last modified: June 17, 2026
Status: Modified

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-18265 in the EU Vulnerability Database. Last updated in EUVD on September 17, 2024.

View on the EU Vulnerability Database

Affected products

juniper / junos
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and 82 more…

Certified products that may be affected

2 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Junos Space Network Management Platform, with or without Network Director and with or without Security Director in JA2500 - Juniper Networks, Inc. - FIPS 140 3816 - historical
Juniper Networks SRX345/SRX345-DUAL-AC with Junos 15.1X49-D110 - Juniper Networks, Inc. - FIPS 140 3247 - historical

References

https://kb.juniper.net/JSA11220(Patch, Vendor Advisory)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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