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CVE-2021-0261

Junos OS: Denial of Service vulnerability in J-Web and web based (HTTP/HTTPS) services caused by a high number of specific requests

High7.5EPSS 1.1%
Published
Updated
Reserved
Assigned by
juniper

Description

A vulnerability in the HTTP/HTTPS service used by J-Web, Web Authentication, Dynamic-VPN (DVPN), Firewall Authentication Pass-Through with Web-Redirect, and Captive Portal allows an unauthenticated attacker to cause an extended Denial of Service (DoS) for these services by sending a high number of specific requests. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S17 on EX Series; 12.3X48 versions prior to 12.3X48-D105 on SRX Series; 15.1 versions prior to 15.1R7-S8; 15.1X49 versions prior to 15.1X49-D230 on SRX Series; 16.1 versions prior to 16.1R7-S8; 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R1-S3, 20.1R2; 20.2 versions prior to 20.2R1-S1, 20.2R2.

Scores

CVSS scores of CVE-2021-0261, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
1.1% · top 34% 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 7.5.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 12.3 – < 12.3R12-S17

  • Juniper Networks · Junos OS

    • affected 12.3X48 – < 12.3X48-D105
    • affected 15.1X49 – < 15.1X49-D230

  • Juniper Networks · Junos OS

    • affected 15.1 – < 15.1R7-S8
    • affected 16.1 – < 16.1R7-S8
    • affected 17.4 – < 17.4R2-S12, 17.4R3-S3
    • affected 18.1 – < 18.1R3-S11
    • affected 18.2 – < 18.2R3-S6
    • affected 18.3 – < 18.3R2-S4, 18.3R3-S3
    • affected 18.4 – < 18.4R2-S5, 18.4R3-S4
    • affected 19.1 – < 19.1R2-S2, 19.1R3-S2
    • affected 19.2 – < 19.2R1-S5, 19.2R3
    • affected 19.3 – < 19.3R2-S4, 19.3R3
    • affected 19.4 – < 19.4R1-S3, 19.4R2-S2, 19.4R3
    • affected 20.1 – < 20.1R1-S3, 20.1R2
    • affected 20.2 – < 20.2R1-S1, 20.2R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 12.3R12-S17, 12.3X48-D105, 15.1R7-S8, 15.1X49-D230, 16.1R7-S8, 17.4R2-S12, 17.4R3-S3, 18.1R3-S11, 18.2R3-S6, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S4, 19.1R2-S2, 19.1R3-S2, 19.2R1-S5, 19.2R3, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2-S2, 19.4R3, 20.1R1-S3, 20.1R2, 20.2R1-S1, 20.2R2, 20.3R1, and all subsequent releases.

Workaround: There are no viable workarounds for this issue other than disabling the web-service: [deactivate system services web-management] To reduce the risk of exploitation utilize common security BCPs to limit the exploitable surface by limiting access to network and device to trusted systems, administrators, networks and hosts. The 'restart web-management' command can be used to restart the web-service to recover from this issue.

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 .