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HIGH · 7.5

CVE-2026-21905

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...

Vulnerability Description

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.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH

Affected Products

VendorProductVersions
JuniperJunos< 21.2
JuniperMx10004-
JuniperMx10008-
JuniperMx2008-
JuniperMx2010-
JuniperMx2020-
JuniperMx204-
JuniperMx240-
JuniperMx304-
JuniperMx480-
JuniperMx960-
JuniperSrx1500-
JuniperSrx1600-
JuniperSrx2300-
JuniperSrx300-
JuniperSrx320-
JuniperSrx340-
JuniperSrx345-
JuniperSrx380-
JuniperSrx4100-

Related Weaknesses (CWE)

CWE-835

References

FAQ

What is CVE-2026-21905?

CVE-2026-21905 is a vulnerability with a CVSS score of 7.5 (HIGH). 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...

How severe is CVE-2026-21905?

CVE-2026-21905 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-21905?

Check the references section above for vendor advisories and patch information. Affected products include: Juniper Junos, Juniper Mx10004, Juniper Mx10008, Juniper Mx2008, Juniper Mx2010.