CVE Vulnerabilities

CVE-2026-21905

Loop with Unreachable Exit Condition ('Infinite Loop')

Published: Jan 15, 2026 | Modified: Jan 23, 2026
CVSS 3.x
N/A
Source:
NVD
CVSS 2.x
RedHat/V2
RedHat/V3
Ubuntu
root.io logo minimus.io logo echo.ai logo

A Loop with Unreachable Exit Condition (Infinite Loop) vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX Series and MX Series with MX-SPC3 or MS-MPC allows an unauthenticated network-based attacker sending specific SIP messages over TCP to crash the flow management process, leading to a Denial of Service (DoS).

On SRX Series, and MX Series with MX-SPC3 or MS-MPC service cards, receipt of multiple SIP messages causes the SIP headers to be parsed incorrectly, eventually causing a continuous loop and leading to a watchdog timer expiration, crashing the flowd process on SRX Series and MX Series with MX-SPC3, or mspmand process on MX Series with MS-MPC.

This issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.

This issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:

  • all versions before 21.2R3-S10, 
  • from 21.4 before 21.4R3-S12, 
  • from 22.4 before 22.4R3-S8, 
  • from 23.2 before 23.2R2-S5, 
  • from 23.4 before 23.4R2-S6, 
  • from 24.2 before 24.2R2-S3, 
  • from 24.4 before 24.4R2-S1, 
  • from 25.2 before 25.2R1-S1, 25.2R2.

Weakness

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

Affected Software

NameVendorStart VersionEnd Version
JunosJuniper*21.2 (excluding)
JunosJuniper21.2 (including)21.2 (including)
JunosJuniper21.2-r1 (including)21.2-r1 (including)
JunosJuniper21.2-r1-s1 (including)21.2-r1-s1 (including)
JunosJuniper21.2-r1-s2 (including)21.2-r1-s2 (including)
JunosJuniper21.2-r2 (including)21.2-r2 (including)
JunosJuniper21.2-r2-s1 (including)21.2-r2-s1 (including)
JunosJuniper21.2-r2-s2 (including)21.2-r2-s2 (including)
JunosJuniper21.2-r3 (including)21.2-r3 (including)
JunosJuniper21.2-r3-s1 (including)21.2-r3-s1 (including)
JunosJuniper21.2-r3-s2 (including)21.2-r3-s2 (including)
JunosJuniper21.2-r3-s3 (including)21.2-r3-s3 (including)
JunosJuniper21.2-r3-s4 (including)21.2-r3-s4 (including)
JunosJuniper21.2-r3-s5 (including)21.2-r3-s5 (including)
JunosJuniper21.2-r3-s6 (including)21.2-r3-s6 (including)
JunosJuniper21.2-r3-s7 (including)21.2-r3-s7 (including)
JunosJuniper21.2-r3-s8 (including)21.2-r3-s8 (including)
JunosJuniper21.2-r3-s9 (including)21.2-r3-s9 (including)
JunosJuniper21.4 (including)21.4 (including)
JunosJuniper21.4-r1 (including)21.4-r1 (including)
JunosJuniper21.4-r1-s1 (including)21.4-r1-s1 (including)
JunosJuniper21.4-r1-s2 (including)21.4-r1-s2 (including)
JunosJuniper21.4-r2 (including)21.4-r2 (including)
JunosJuniper21.4-r2-s1 (including)21.4-r2-s1 (including)
JunosJuniper21.4-r2-s2 (including)21.4-r2-s2 (including)
JunosJuniper21.4-r3 (including)21.4-r3 (including)
JunosJuniper21.4-r3-s1 (including)21.4-r3-s1 (including)
JunosJuniper21.4-r3-s10 (including)21.4-r3-s10 (including)
JunosJuniper21.4-r3-s11 (including)21.4-r3-s11 (including)
JunosJuniper21.4-r3-s2 (including)21.4-r3-s2 (including)
JunosJuniper21.4-r3-s3 (including)21.4-r3-s3 (including)
JunosJuniper21.4-r3-s4 (including)21.4-r3-s4 (including)
JunosJuniper21.4-r3-s5 (including)21.4-r3-s5 (including)
JunosJuniper21.4-r3-s6 (including)21.4-r3-s6 (including)
JunosJuniper21.4-r3-s7 (including)21.4-r3-s7 (including)
JunosJuniper21.4-r3-s8 (including)21.4-r3-s8 (including)
JunosJuniper21.4-r3-s9 (including)21.4-r3-s9 (including)
JunosJuniper22.4 (including)22.4 (including)
JunosJuniper22.4-r1 (including)22.4-r1 (including)
JunosJuniper22.4-r1-s1 (including)22.4-r1-s1 (including)
JunosJuniper22.4-r1-s2 (including)22.4-r1-s2 (including)
JunosJuniper22.4-r2 (including)22.4-r2 (including)
JunosJuniper22.4-r2-s1 (including)22.4-r2-s1 (including)
JunosJuniper22.4-r2-s2 (including)22.4-r2-s2 (including)
JunosJuniper22.4-r3 (including)22.4-r3 (including)
JunosJuniper22.4-r3-s1 (including)22.4-r3-s1 (including)
JunosJuniper22.4-r3-s2 (including)22.4-r3-s2 (including)
JunosJuniper22.4-r3-s3 (including)22.4-r3-s3 (including)
JunosJuniper22.4-r3-s4 (including)22.4-r3-s4 (including)
JunosJuniper22.4-r3-s5 (including)22.4-r3-s5 (including)
JunosJuniper22.4-r3-s6 (including)22.4-r3-s6 (including)
JunosJuniper22.4-r3-s7 (including)22.4-r3-s7 (including)
JunosJuniper23.2 (including)23.2 (including)
JunosJuniper23.2-r1 (including)23.2-r1 (including)
JunosJuniper23.2-r1-s1 (including)23.2-r1-s1 (including)
JunosJuniper23.2-r1-s2 (including)23.2-r1-s2 (including)
JunosJuniper23.2-r2 (including)23.2-r2 (including)
JunosJuniper23.2-r2-s1 (including)23.2-r2-s1 (including)
JunosJuniper23.2-r2-s2 (including)23.2-r2-s2 (including)
JunosJuniper23.2-r2-s3 (including)23.2-r2-s3 (including)
JunosJuniper23.2-r2-s4 (including)23.2-r2-s4 (including)
JunosJuniper23.4 (including)23.4 (including)
JunosJuniper23.4-r1 (including)23.4-r1 (including)
JunosJuniper23.4-r1-s1 (including)23.4-r1-s1 (including)
JunosJuniper23.4-r1-s2 (including)23.4-r1-s2 (including)
JunosJuniper23.4-r2 (including)23.4-r2 (including)
JunosJuniper23.4-r2-s1 (including)23.4-r2-s1 (including)
JunosJuniper23.4-r2-s2 (including)23.4-r2-s2 (including)
JunosJuniper23.4-r2-s3 (including)23.4-r2-s3 (including)
JunosJuniper23.4-r2-s4 (including)23.4-r2-s4 (including)
JunosJuniper23.4-r2-s5 (including)23.4-r2-s5 (including)
JunosJuniper24.2 (including)24.2 (including)
JunosJuniper24.2-r1 (including)24.2-r1 (including)
JunosJuniper24.2-r1-s1 (including)24.2-r1-s1 (including)
JunosJuniper24.2-r1-s2 (including)24.2-r1-s2 (including)
JunosJuniper24.2-r2 (including)24.2-r2 (including)
JunosJuniper24.2-r2-s1 (including)24.2-r2-s1 (including)
JunosJuniper24.2-r2-s2 (including)24.2-r2-s2 (including)
JunosJuniper24.4 (including)24.4 (including)
JunosJuniper24.4-r1 (including)24.4-r1 (including)
JunosJuniper24.4-r1-s2 (including)24.4-r1-s2 (including)
JunosJuniper24.4-r1-s3 (including)24.4-r1-s3 (including)
JunosJuniper24.4-r2 (including)24.4-r2 (including)
JunosJuniper25.2 (including)25.2 (including)
JunosJuniper25.2-r1 (including)25.2-r1 (including)
JunosJuniper25.2-r2 (including)25.2-r2 (including)

References