CVE-2026-21905
Severity CVSS v4.0:
HIGH
Type:
Unavailable / Other
Publication date:
15/01/2026
Last modified:
15/01/2026
Description
A Loop with Unreachable Exit Condition (&#39;Infinite Loop&#39;) 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).<br />
<br />
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.<br />
<br />
This issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.<br />
<br />
This issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:<br />
<br />
<br />
<br />
* all versions before 21.2R3-S10, <br />
* from 21.4 before 21.4R3-S12, <br />
* from 22.4 before 22.4R3-S8, <br />
* from 23.2 before 23.2R2-S5, <br />
* from 23.4 before 23.4R2-S6, <br />
* from 24.2 before 24.2R2-S3, <br />
* from 24.4 before 24.4R2-S1, <br />
* from 25.2 before 25.2R1-S1, 25.2R2.
Impact
Base Score 4.0
8.70
Severity 4.0
HIGH
Base Score 3.x
7.50
Severity 3.x
HIGH