What is the CVSS score of CVE-2026-21905?

CVE-2026-21905 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.0%.

Which versions of Junos are affected by CVE-2026-21905?

CVE-2026-21905 presents notable security risk rated CVSS 7.5. Exploitation could compromise the security of affected deployments.

How to fix or mitigate CVE-2026-21905?

Within 7 days: Identify all affected systems and apply vendor patches promptly. Monitor vendor channels for patch availability.

Junos CVE-2026-21905

HIGH

Loop with Unreachable Exit Condition (Infinite Loop) (CWE-835)

2026-01-15 sirt@juniper.net

Juniper Denial Of Service Junos

7.5

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Jan 15, 2026 - 21:16 nvd

HIGH 7.5

DescriptionCVE.org

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.

AnalysisAI

Denial of service in Juniper Junos SIP application layer gateway allows unauthenticated remote attackers to crash critical processes by sending malformed SIP messages over TCP, affecting SRX Series and MX Series devices with specific service cards. The vulnerability exploits improper header parsing that triggers an infinite loop and watchdog timer expiration, disabling network traffic flow without requiring authentication or user interaction. No patch is currently available for this high-severity flaw.

Technical ContextAI

This vulnerability (CWE-835: Loop with Unreachable Exit Condition (Infinite Loop)) affects Junos. 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 incor