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CVE-2021-31373

Junos OS: SRX Series: Persistent XSS vulnerability in J-Web

High8.0EPSS 0.81%
Published
Updated
Reserved
Assigned by
juniper

Description

A persistent Cross-Site Scripting (XSS) vulnerability in Juniper Networks Junos OS on SRX Series, J-Web interface may allow a remote authenticated user to inject persistent and malicious scripts. An attacker can exploit this vulnerability to steal sensitive data and credentials from a web administration session, or hijack another user's active session to perform administrative actions. This issue affects: Juniper Networks Junos OS on SRX Series: 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R2-S1, 20.3R3.

Scores

CVSS scores of CVE-2021-31373, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High8.0CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
NVDNVD · Modified3.1Medium5.4CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS (exploitation in 30 days)
0.81% · top 43% of all CVEs (6 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.0.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 18.2 – < 18.2R3-S8
    • affected 18.3 – < 18.3R3-S5
    • affected 18.4 – < 18.4R3-S8
    • affected 19.1 – < 19.1R3-S5
    • affected 19.2 – < 19.2R1-S7, 19.2R3-S3
    • affected 19.3 – < 19.3R2-S6, 19.3R3-S3
    • affected 19.4 – < 19.4R1-S4, 19.4R2-S4, 19.4R3-S3
    • affected 20.1 – < 20.1R2-S2, 20.1R3
    • affected 20.2 – < 20.2R3-S1
    • affected 20.3 – < 20.3R2-S1, 20.3R3

What to do

Solution: The following software releases have been updated to resolve this specific issue: 18.2R3-S8, 18.3R3-S5, 18.4R3-S8, 19.1R3-S5, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R2-S4, 19.4R3-S3, 20.1R2-S2, 20.1R3, 20.2R3-S1, 20.3R2-S1, 20.3R3, 20.4R1, and all subsequent releases.

Workaround: To reduce the risk of exploitation of this issue, use access lists or firewall filters to limit access to only trusted administrative networks, hosts and users. Alternatively, J-Web can be disabled.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .