Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2021-0261 — juniper / junos

Out-of-bounds Read

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.

  • Published: Apr 22, 2021
  • Updated: Nov 16, 2025
  • CVE: CVE-2021-0261
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 7.5
  • AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2:

  • Severity: Medium
  • Score: 5
  • AV:N/AC:L/Au:N/C:N/I:N/A:P
Software From Fixed in
juniper / junos 12.3-r11 12.3-r11.x
juniper / junos 12.3-r1 12.3-r1.x
juniper / junos 12.3-r12 12.3-r12.x
juniper / junos 12.3-r10 12.3-r10.x
juniper / junos 12.3-r12-s10 12.3-r12-s10.x
juniper / junos 12.3-r12-s8 12.3-r12-s8.x
juniper / junos 12.3 12.3.x
juniper / junos 12.3-r12-s13 12.3-r12-s13.x
juniper / junos 12.3-r12-s14 12.3-r12-s14.x
juniper / junos 12.3-r12-s1 12.3-r12-s1.x
juniper / junos 12.3-r12-s3 12.3-r12-s3.x
juniper / junos 12.3-r12-s4 12.3-r12-s4.x
juniper / junos 12.3-r12-s6 12.3-r12-s6.x
juniper / junos 12.3-r12-s11 12.3-r12-s11.x
juniper / junos 12.3-r12-s12 12.3-r12-s12.x
juniper / junos 12.3-r10-s1 12.3-r10-s1.x
juniper / junos 12.3-r10-s2 12.3-r10-s2.x
juniper / junos 12.3-r12-s15 12.3-r12-s15.x
juniper / junos 12.3-r12-s16 12.3-r12-s16.x
juniper / junos 12.3x48-d15 12.3x48-d15.x
juniper / junos 12.3x48-d35 12.3x48-d35.x
juniper / junos 12.3x48-d50 12.3x48-d50.x
juniper / junos 12.3x48-d30 12.3x48-d30.x
juniper / junos 12.3x48-d25 12.3x48-d25.x
juniper / junos 12.3x48-d45 12.3x48-d45.x
juniper / junos 12.3x48-d55 12.3x48-d55.x
juniper / junos 12.3x48-d20 12.3x48-d20.x
juniper / junos 12.3x48-d10 12.3x48-d10.x
juniper / junos 12.3x48-d40 12.3x48-d40.x
juniper / junos 12.3x48-d60 12.3x48-d60.x
juniper / junos 12.3x48-d65 12.3x48-d65.x
juniper / junos 12.3x48-d70 12.3x48-d70.x
juniper / junos 12.3x48-d75 12.3x48-d75.x
juniper / junos 12.3x48-d66 12.3x48-d66.x
juniper / junos 12.3x48-d51 12.3x48-d51.x
juniper / junos 12.3x48-d80 12.3x48-d80.x
juniper / junos 12.3x48 12.3x48.x
juniper / junos 12.3x48-d85 12.3x48-d85.x
juniper / junos 12.3x48-d95 12.3x48-d95.x
juniper / junos 12.3x48-d90 12.3x48-d90.x
juniper / junos 12.3x48-d100 12.3x48-d100.x
juniper / junos 15.1x49-d190 15.1x49-d190.x
juniper / junos 15.1x49-d200 15.1x49-d200.x
juniper / junos 15.1x49-d210 15.1x49-d210.x
juniper / junos 15.1x49 15.1x49.x
juniper / junos 15.1x49-d180 15.1x49-d180.x
juniper / junos 15.1x49-d170 15.1x49-d170.x
juniper / junos 15.1x49-d150 15.1x49-d150.x
juniper / junos 15.1x49-d131 15.1x49-d131.x
juniper / junos 15.1x49-d160 15.1x49-d160.x
juniper / junos 15.1x49-d140 15.1x49-d140.x
juniper / junos 15.1x49-d120 15.1x49-d120.x
juniper / junos 15.1x49-d130 15.1x49-d130.x
juniper / junos 15.1x49-d25 15.1x49-d25.x
juniper / junos 15.1x49-d110 15.1x49-d110.x
juniper / junos 15.1x49-d60 15.1x49-d60.x
juniper / junos 15.1x49-d20 15.1x49-d20.x
juniper / junos 15.1x49-d10 15.1x49-d10.x
juniper / junos 15.1x49-d55 15.1x49-d55.x
juniper / junos 15.1x49-d15 15.1x49-d15.x
juniper / junos 15.1x49-d40 15.1x49-d40.x
juniper / junos 15.1x49-d35 15.1x49-d35.x
juniper / junos 15.1x49-d45 15.1x49-d45.x
juniper / junos 15.1x49-d75 15.1x49-d75.x
juniper / junos 15.1x49-d65 15.1x49-d65.x
juniper / junos 15.1x49-d90 15.1x49-d90.x
juniper / junos 15.1x49-d100 15.1x49-d100.x
juniper / junos 15.1x49-d50 15.1x49-d50.x
juniper / junos 15.1x49-d30 15.1x49-d30.x
juniper / junos 15.1x49-d70 15.1x49-d70.x
juniper / junos 15.1x49-d80 15.1x49-d80.x
juniper / junos 15.1-r7 15.1-r7.x
juniper / junos 16.1-r 16.1-r.x
juniper / junos 15.1-f1 15.1-f1.x
juniper / junos 15.1-f6-s4 15.1-f6-s4.x
juniper / junos 15.1-f2-s3 15.1-f2-s3.x
juniper / junos 15.1-f7 15.1-f7.x
juniper / junos 16.1-r1 16.1-r1.x
juniper / junos 15.1-r3 15.1-r3.x
juniper / junos 15.1-r 15.1-r.x
juniper / junos 15.1-f2-s2 15.1-f2-s2.x
juniper / junos 15.1-r6 15.1-r6.x
juniper / junos 15.1-f4 15.1-f4.x
juniper / junos 15.1-r4 15.1-r4.x
juniper / junos 15.1-f2-s4 15.1-f2-s4.x
juniper / junos 15.1-f5-s7 15.1-f5-s7.x
juniper / junos 15.1-f6-s7 15.1-f6-s7.x
juniper / junos 15.1-f6 15.1-f6.x
juniper / junos 15.1-f2 15.1-f2.x
juniper / junos 15.1-a1 15.1-a1.x
juniper / junos 16.1-r4-s4 16.1-r4-s4.x
juniper / junos 15.1-f3 15.1-f3.x
juniper / junos 15.1-r2 15.1-r2.x
juniper / junos 16.1-r4 16.1-r4.x
juniper / junos 15.1-r4-s7 15.1-r4-s7.x
juniper / junos 15.1-r4-s8 15.1-r4-s8.x
juniper / junos 16.1-r4-s3 16.1-r4-s3.x
juniper / junos 15.1-r5-s5 15.1-r5-s5.x
juniper / junos 15.1-r6-s1 15.1-r6-s1.x
juniper / junos 15.1-r5 15.1-r5.x
juniper / junos 15.1-r1 15.1-r1.x
juniper / junos 15.1-f2-s1 15.1-f2-s1.x
juniper / junos 15.1-r5-s1 15.1-r5-s1.x
juniper / junos 15.1-f5 15.1-f5.x
juniper / junos 16.1-r3 16.1-r3.x
juniper / junos 16.1-r5 16.1-r5.x
juniper / junos 16.1-r2 16.1-r2.x
juniper / junos 15.1-f6-s8 15.1-f6-s8.x
juniper / junos 15.1-r5-s3 15.1-r5-s3.x
juniper / junos 16.1-r6 16.1-r6.x
juniper / junos 17.3-r1 17.3-r1.x
juniper / junos 15.1-r5-s6 15.1-r5-s6.x
juniper / junos 15.1-r6-s2 15.1-r6-s2.x
juniper / junos 15.1-r6-s3 15.1-r6-s3.x
juniper / junos 15.1-r6-s4 15.1-r6-s4.x
juniper / junos 15.1-f6-s9 15.1-f6-s9.x
juniper / junos 15.1-r4-s9 15.1-r4-s9.x
juniper / junos 15.1-r6-s6 15.1-r6-s6.x
juniper / junos 16.1-r5-s4 16.1-r5-s4.x
juniper / junos 16.1-r6-s1 16.1-r6-s1.x
juniper / junos 16.1-r7 16.1-r7.x
juniper / junos 17.3-r2 17.3-r2.x
juniper / junos 17.4-r1 17.4-r1.x
juniper / junos 17.4-r2 17.4-r2.x
juniper / junos 15.1-f 15.1-f.x
juniper / junos 16.1-r4-s9 16.1-r4-s9.x
juniper / junos 16.1-r6-s3 16.1-r6-s3.x
juniper / junos 17.3-r2-s2 17.3-r2-s2.x
juniper / junos 17.3-r3 17.3-r3.x
juniper / junos 18.1-r1 18.1-r1.x
juniper / junos 15.1-f6-s3 15.1-f6-s3.x
juniper / junos 16.1-r4-s8 16.1-r4-s8.x
juniper / junos 18.1-r3 18.1-r3.x
juniper / junos 15.1-r7-s1 15.1-r7-s1.x
juniper / junos 16.1-r6-s4 16.1-r6-s4.x
juniper / junos 16.1-r6-s6 16.1-r6-s6.x
juniper / junos 15.1-f6-s10 15.1-f6-s10.x
juniper / junos 16.1-r3-s8 16.1-r3-s8.x
juniper / junos 17.3-r1-s4 17.3-r1-s4.x
juniper / junos 17.4-r1-s3 17.4-r1-s3.x
juniper / junos 18.1-r2 18.1-r2.x
juniper / junos 18.2-r1 18.2-r1.x
juniper / junos 16.1-r3-s10 16.1-r3-s10.x
juniper / junos 15.1-r7-s2 15.1-r7-s2.x
juniper / junos 15.1-r7-s3 15.1-r7-s3.x
juniper / junos 17.4-r2-s2 17.4-r2-s2.x
juniper / junos 17.4-r1-s1 17.4-r1-s1.x
juniper / junos 18.2 18.2.x
juniper / junos 18.2-r2-s1 18.2-r2-s1.x
juniper / junos 18.2-r2-s2 18.2-r2-s2.x
juniper / junos 18.2-r1-s3 18.2-r1-s3.x
juniper / junos 18.3-r1-s1 18.3-r1-s1.x
juniper / junos 17.3-r3-s1 17.3-r3-s1.x
juniper / junos 17.3-r3-s2 17.3-r3-s2.x
juniper / junos 17.4-r1-s2 17.4-r1-s2.x
juniper / junos 17.3-r2-s1 17.3-r2-s1.x
juniper / junos 18.3-r2 18.3-r2.x
juniper / junos 18.3-r1 18.3-r1.x
juniper / junos 17.4-r2-s1 17.4-r2-s1.x
juniper / junos 18.1-r2-s2 18.1-r2-s2.x
juniper / junos 15.1-f6-s2 15.1-f6-s2.x
juniper / junos 15.1-f6-s1 15.1-f6-s1.x
juniper / junos 15.1-f6-s5 15.1-f6-s5.x
juniper / junos 15.1-f6-s6 15.1-f6-s6.x
juniper / junos 18.4-r1 18.4-r1.x
juniper / junos 17.4 17.4.x
juniper / junos 18.1-r3-s4 18.1-r3-s4.x
juniper / junos 18.1-r3-s3 18.1-r3-s3.x
juniper / junos 18.1-r3-s2 18.1-r3-s2.x
juniper / junos 18.1 18.1.x
juniper / junos 18.1-r2-s1 18.1-r2-s1.x
juniper / junos 18.1-r2-s4 18.1-r2-s4.x
juniper / junos 15.1 15.1.x
juniper / junos 16.1 16.1.x
juniper / junos 17.3 17.3.x
juniper / junos 18.3-r1-s2 18.3-r1-s2.x
juniper / junos 18.3 18.3.x
juniper / junos 18.4 18.4.x
juniper / junos 17.4-r1-s5 17.4-r1-s5.x
juniper / junos 18.1-r3-s1 18.1-r3-s1.x
juniper / junos 17.3-r3-s3 17.3-r3-s3.x
juniper / junos 17.4-r1-s7 17.4-r1-s7.x
juniper / junos 16.1-r3-s11 16.1-r3-s11.x
juniper / junos 17.4-r1-s4 17.4-r1-s4.x
juniper / junos 18.4-r1-s1 18.4-r1-s1.x
juniper / junos 17.3-r3-s4 17.3-r3-s4.x
juniper / junos 17.3-r3-s5 17.3-r3-s5.x
juniper / junos 17.4-r2-s3 17.4-r2-s3.x
juniper / junos 17.4-r2-s4 17.4-r2-s4.x
juniper / junos 17.4-r1-s6 17.4-r1-s6.x
juniper / junos 18.1-r3-s5 18.1-r3-s5.x
juniper / junos 18.3-r1-s3 18.3-r1-s3.x
juniper / junos 18.2-r2-s3 18.2-r2-s3.x
juniper / junos 18.2-r2-s4 18.2-r2-s4.x
juniper / junos 18.3-r1-s4 18.3-r1-s4.x
juniper / junos 18.2-r1-s4 18.2-r1-s4.x
juniper / junos 18.2-r1-s5 18.2-r1-s5.x
juniper / junos 18.2-r2 18.2-r2.x
juniper / junos 17.3-r3-s6 17.3-r3-s6.x
juniper / junos 18.4-r1-s3 18.4-r1-s3.x
juniper / junos 18.4-r1-s4 18.4-r1-s4.x
juniper / junos 18.4-r1-s2 18.4-r1-s2.x
juniper / junos 19.1-r1 19.1-r1.x
juniper / junos 19.1 19.1.x
juniper / junos 17.3-r2-s3 17.3-r2-s3.x
juniper / junos 16.1-r7-s3 16.1-r7-s3.x
juniper / junos 16.1-r7-s4 16.1-r7-s4.x
juniper / junos 17.4-r2-s5 17.4-r2-s5.x
juniper / junos 17.4-r2-s6 17.4-r2-s6.x
juniper / junos 17.4-r2-s7 17.4-r2-s7.x
juniper / junos 19.2-r1 19.2-r1.x
juniper / junos 18.4-r2 18.4-r2.x
juniper / junos 18.2-r3 18.2-r3.x
juniper / junos 18.1-r3-s6 18.1-r3-s6.x
juniper / junos 18.1-r3-s7 18.1-r3-s7.x
juniper / junos 19.1-r1-s1 19.1-r1-s1.x
juniper / junos 19.1-r1-s3 19.1-r1-s3.x
juniper / junos 19.1-r1-s2 19.1-r1-s2.x
juniper / junos 15.1-r7-s4 15.1-r7-s4.x
juniper / junos 17.3-r1-s1 17.3-r1-s1.x
juniper / junos 15.1-r7-s5 15.1-r7-s5.x
juniper / junos 16.1-r7-s2 16.1-r7-s2.x
juniper / junos 18.2-r2-s5 18.2-r2-s5.x
juniper / junos 18.2-r2-s6 18.2-r2-s6.x
juniper / junos 18.4-r1-s5 18.4-r1-s5.x
juniper / junos 15.1-f6-s12 15.1-f6-s12.x
juniper / junos 19.2-r1-s1 19.2-r1-s1.x
juniper / junos 19.2-r1-s2 19.2-r1-s2.x
juniper / junos 18.3-r1-s5 18.3-r1-s5.x
juniper / junos 18.2-r3-s1 18.2-r3-s1.x
juniper / junos 16.1-r7-s5 16.1-r7-s5.x
juniper / junos 16.1-r4-s12 16.1-r4-s12.x
juniper / junos 16.1-r4-s6 16.1-r4-s6.x
juniper / junos 16.1-r4-s2 16.1-r4-s2.x
juniper / junos 17.3-r2-s4 17.3-r2-s4.x
juniper / junos 18.3-r2-s1 18.3-r2-s1.x
juniper / junos 18.3-r2-s2 18.3-r2-s2.x
juniper / junos 17.4-r2-s8 17.4-r2-s8.x
juniper / junos 18.4-r2-s1 18.4-r2-s1.x
juniper / junos 19.3 19.3.x
juniper / junos 19.3-r1 19.3-r1.x
juniper / junos 19.2 19.2.x
juniper / junos 18.4-r2-s2 18.4-r2-s2.x
juniper / junos 18.3-r1-s6 18.3-r1-s6.x
juniper / junos 18.2-r3-s2 18.2-r3-s2.x
juniper / junos 18.1-r3-s8 18.1-r3-s8.x
juniper / junos 19.2-r1-s3 19.2-r1-s3.x
juniper / junos 18.3-r3 18.3-r3.x
juniper / junos 16.1-r7-s6 16.1-r7-s6.x
juniper / junos 19.4-r1 19.4-r1.x
juniper / junos 19.3-r2 19.3-r2.x
juniper / junos 19.1-r2 19.1-r2.x
juniper / junos 18.4-r3 18.4-r3.x
juniper / junos 18.4-r2-s3 18.4-r2-s3.x
juniper / junos 18.3-r3-s1 18.3-r3-s1.x
juniper / junos 18.1-r3-s9 18.1-r3-s9.x
juniper / junos 17.3-r3-s7 17.3-r3-s7.x
juniper / junos 19.3-r2-s1 19.3-r2-s1.x
juniper / junos 19.3-r1-s1 19.3-r1-s1.x
juniper / junos 19.2-r1-s4 19.2-r1-s4.x
juniper / junos 20.1-r1 20.1-r1.x
juniper / junos 19.4-r1-s1 19.4-r1-s1.x
juniper / junos 19.3-r2-s2 19.3-r2-s2.x
juniper / junos 19.1-r1-s4 19.1-r1-s4.x
juniper / junos 18.4-r1-s6 18.4-r1-s6.x
juniper / junos 18.3-r2-s3 18.3-r2-s3.x
juniper / junos 18.2-r3-s3 18.2-r3-s3.x
juniper / junos 17.4-r2-s9 17.4-r2-s9.x
juniper / junos 17.4-r2-s10 17.4-r2-s10.x
juniper / junos 16.1-r7-s7 16.1-r7-s7.x
juniper / junos 15.1-r7-s7 15.1-r7-s7.x
juniper / junos 18.2-r3-s4 18.2-r3-s4.x
juniper / junos 17.3-r2-s5 17.3-r2-s5.x
juniper / junos 18.4-r3-s2 18.4-r3-s2.x
juniper / junos 18.4-r3-s1 18.4-r3-s1.x
juniper / junos 18.4-r2-s4 18.4-r2-s4.x
juniper / junos 19.1-r2-s1 19.1-r2-s1.x
juniper / junos 19.1-r3 19.1-r3.x
juniper / junos 19.1-r3-s1 19.1-r3-s1.x
juniper / junos 15.1-r7-s6 15.1-r7-s6.x
juniper / junos 19.4-r1-s2 19.4-r1-s2.x
juniper / junos 20.1-r1-s1 20.1-r1-s1.x
juniper / junos 20.2-r1 20.2-r1.x
juniper / junos 20.1-r1-s2 20.1-r1-s2.x
juniper / junos 19.4-r2 19.4-r2.x
juniper / junos 19.4-r2-s1 19.4-r2-s1.x
juniper / junos 19.3-r2-s3 19.3-r2-s3.x
juniper / junos 18.4-r3-s3 18.4-r3-s3.x
juniper / junos 18.2-r3-s5 18.2-r3-s5.x
juniper / junos 18.1-r3-s10 18.1-r3-s10.x
juniper / junos 18.3-r3-s2 18.3-r3-s2.x
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Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.