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

HIGH

7.5

CVSS Score

Published: April 22, 2021 at 07:37 PM UTC

Updated: June 17, 2026 at 03:29 AM UTC

23 products affected across 2 vendorsJunosSRX5600SRX5800

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Severity

HIGH7.5

Exploit prediction

EPSS 1%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

12.3 ≤ v < 12.3R12-S1712.3X48 ≤ v < 12.3X48-D10515.1 ≤ v < 15.1R7-S815.1X49 ≤ v < 15.1X49-D23016.1 ≤ v < 16.1R7-S817.4 ≤ v < 17.4R2-S12, 17.4R3-S318.1 ≤ v < 18.1R3-S1118.2 ≤ v < 18.2R3-S618.3 ≤ v < 18.3R2-S4, 18.3R3-S318.4 ≤ v < 18.4R2-S5, 18.4R3-S419.1 ≤ v < 19.1R2-S2, 19.1R3-S219.2 ≤ v < 19.2R1-S5, 19.2R319.3 ≤ v < 19.3R2-S4, 19.3R319.4 ≤ v < 19.4R1-S3, 19.4R2-S2, 19.4R320.1 ≤ v < 20.1R1-S3, 20.1R220.2 ≤ v < 20.2R1-S1, 20.2R212.3 12.3 r1 12.3 r10 12.3 r10-s1 12.3 r10-s2 12.3 r11 12.3 r12 12.3 r12-s1 12.3 r12-s10 12.3 r12-s11 12.3 r12-s12 12.3 r12-s13 12.3 r12-s14 12.3 r12-s15 12.3 r12-s16 12.3 r12-s3 12.3 r12-s4 12.3 r12-s6 12.3 r12-s8 12.3X4812.3x4812.3x48 d10 12.3x48 d100 12.3x48 d15 12.3x48 d20 12.3x48 d25 12.3x48 d30 12.3x48 d35 12.3x48 d40 12.3x48 d45 12.3x48 d50 12.3x48 d51 12.3x48 d55 12.3x48 d60 12.3x48 d6512.3x48 d6612.3x48 d70 12.3x48 d7512.3x48 d8012.3x48 d85 12.3x48 d90 12.3x48 d95 15.1 15.1 a1 15.1 f 15.1 f1 15.1 f2 15.1 f2-s1 15.1 f2-s2 15.1 f2-s3 15.1 f2-s4 15.1 f3 15.1 f4 15.1 f5 15.1 f5-s7 15.1 f6 15.1 f6-s1 15.1 f6-s10 15.1 f6-s12 15.1 f6-s2 15.1 f6-s3 15.1 f6-s4 15.1 f6-s5 15.1 f6-s6 15.1 f6-s7 15.1 f6-s8 15.1 f6-s9 15.1 f7 15.1 r 15.1 r1 15.1 r2 15.1 r3 15.1 r4 15.1 r4-s7 15.1 r4-s8 15.1 r4-s9 15.1 r5 15.1 r5-s1 15.1 r5-s3 15.1 r5-s5 15.1 r5-s6 15.1 r6 15.1 r6-s1 15.1 r6-s2 15.1 r6-s3 15.1 r6-s4 15.1 r6-s6 15.1 r7 15.1 r7-s1 15.1 r7-s2 15.1 r7-s3 15.1 r7-s4 15.1 r7-s5 15.1 r7-s6 15.1 r7-s7 15.1X4915.1x4915.1x49 d10 15.1x49 d100 15.1x49 d110 15.1x49 d120 15.1x49 d13015.1x49 d13115.1x49 d140 15.1x49 d15 15.1x49 d150 15.1x49 d160 15.1x49 d170 15.1x49 d180 15.1x49 d190 15.1x49 d20 15.1x49 d200 15.1x49 d210 15.1x49 d25 15.1x49 d30 15.1x49 d35 15.1x49 d40 15.1x49 d45 15.1x49 d50 15.1x49 d55 15.1x49 d60 15.1x49 d65 15.1x49 d70 15.1x49 d75 15.1x49 d80 15.1x49 d90 16.1 16.1 r 16.1 r1 16.1 r2 16.1 r3 16.1 r3-s10 16.1 r3-s11 16.1 r3-s8 16.1 r4 16.1 r4-s12 16.1 r4-s2 16.1 r4-s3 16.1 r4-s4 16.1 r4-s6 16.1 r4-s8 16.1 r4-s9 16.1 r5 16.1 r5-s4 16.1 r6 16.1 r6-s1 16.1 r6-s3 16.1 r6-s4 16.1 r6-s6 16.1 r7 16.1 r7-s2 16.1 r7-s3 16.1 r7-s4 16.1 r7-s5 16.1 r7-s6 16.1 r7-s7 17.3 17.3 r1 17.3 r1-s1 17.3 r1-s4 17.3 r2 17.3 r2-s1 17.3 r2-s2 17.3 r2-s3 17.3 r2-s4 17.3 r2-s5 17.3 r3 17.3 r3-s1 17.3 r3-s2 17.3 r3-s3 17.3 r3-s4 17.3 r3-s5 17.3 r3-s6 17.3 r3-s7 17.3 r3-s8 17.3 r3-s9 17.4 17.4 r1 17.4 r1-s1 17.4 r1-s2 17.4 r1-s3 17.4 r1-s4 17.4 r1-s5 17.4 r1-s6 17.4 r1-s7 17.4 r2 17.4 r2-s1 17.4 r2-s10 17.4 r2-s11 17.4 r2-s2 17.4 r2-s3 17.4 r2-s4 17.4 r2-s5 17.4 r2-s6 17.4 r2-s7 17.4 r2-s8 17.4 r2-s9 18.1 18.1 r1 18.1 r2 18.1 r2-s1 18.1 r2-s2 18.1 r2-s4 18.1 r3 18.1 r3-s1 18.1 r3-s10 18.1 r3-s2 18.1 r3-s3 18.1 r3-s4 18.1 r3-s5 18.1 r3-s6 18.1 r3-s7 18.1 r3-s8 18.1 r3-s9 18.2 18.2 r1 18.2 r1-s2 18.2 r1-s3 18.2 r1-s4 18.2 r1-s5 18.2 r2 18.2 r2-s1 18.2 r2-s2 18.2 r2-s3 18.2 r2-s4 18.2 r2-s5 18.2 r2-s6 18.2 r2-s7 18.2 r3 18.2 r3-s1 18.2 r3-s2 18.2 r3-s3 18.2 r3-s4 18.2 r3-s5 18.3 18.3 r1 18.3 r1-s1 18.3 r1-s2 18.3 r1-s3 18.3 r1-s4 18.3 r1-s5 18.3 r1-s6 18.3 r2 18.3 r2-s1 18.3 r2-s2 18.3 r2-s3 18.3 r3 18.3 r3-s1 18.3 r3-s2 18.4 18.4 r1 18.4 r1-s1 18.4 r1-s2 18.4 r1-s3 18.4 r1-s4 18.4 r1-s5 18.4 r1-s6 18.4 r1-s7 18.4 r2 18.4 r2-s1 18.4 r2-s2 18.4 r2-s3 18.4 r2-s4 18.4 r3 18.4 r3-s1 18.4 r3-s2 18.4 r3-s3 19.1 19.1 r1 19.1 r1-s1 19.1 r1-s2 19.1 r1-s3 19.1 r1-s4 19.1 r1-s5 19.1 r2 19.1 r2-s1 19.1 r3 19.1 r3-s1 19.2 19.2 r1 19.2 r1-s1 19.2 r1-s2 19.2 r1-s3 19.2 r1-s4 19.2 r2 19.2 r2-s1 19.3 19.3 r1 19.3 r1-s1 19.3 r2 19.3 r2-s1 19.3 r2-s2 19.3 r2-s3 19.4 19.4 r1 19.4 r1-s1 19.4 r1-s2 19.4 r2 19.4 r2-s1 20.1 20.1 r1 20.1 r1-s1 20.1 r1-s2 20.2 20.2 r1

Affected range stops below 12.3R12-S17, so it looks safe — our inference, not a vendor statement

Affected range stops below 12.3X48-D105, so it looks safe — our inference, not a vendor statement

Affected range stops below 15.1R7-S8, so it looks safe — our inference, not a vendor statement

Affected range stops below 15.1X49-D230, so it looks safe — our inference, not a vendor statement

Affected range stops below 16.1R7-S8, so it looks safe — our inference, not a vendor statement

Affected range stops below 17.4R2-S12, 17.4R3-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 18.1R3-S11, so it looks safe — our inference, not a vendor statement

Affected range stops below 18.2R3-S6, so it looks safe — our inference, not a vendor statement

Affected range stops below 18.3R2-S4, 18.3R3-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 18.4R2-S5, 18.4R3-S4, so it looks safe — our inference, not a vendor statement

Affected range stops below 19.1R2-S2, 19.1R3-S2, so it looks safe — our inference, not a vendor statement

Affected range stops below 19.2R1-S5, 19.2R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 19.3R2-S4, 19.3R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 19.4R1-S3, 19.4R2-S2, 19.4R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.1R1-S3, 20.1R2, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.2R1-S1, 20.2R2, so it looks safe — our inference, not a vendor statement

juniper-ex2300 (environment) · juniper-ex2300-c (environment) · juniper-ex3400 (environment) · juniper-ex4300 (environment) · juniper-ex4400 (environment) · juniper-ex4600 (environment) · juniper-ex4650 (environment) · juniper-ex9200 (environment) · juniper-ex9250 (environment) · juniper-srx1500 (environment) · juniper-srx300 (environment) · juniper-srx320 (environment) · juniper-srx340 (environment) · juniper-srx345 (environment) · juniper-srx380 (environment) · juniper-srx4100 (environment) · juniper-srx4200 (environment) · juniper-srx4600 (environment) · juniper-srx5400 (environment) · juniper-srx550 (environment) · juniper-srx5600 (environment) · juniper-srx5800 (environment)

Ex2300 · Juniperdevice

80%

All versions

Ex2300-C · Juniperdevice

80%

All versions

Ex3400 · Juniperdevice

80%

All versions

Ex4300 · Juniperdevice

80%

All versions