CVE-2026-21905

Junos OS: SRX Series, MX Series with MX-SPC3 or MS-MPC: Receipt of multiple specific SIP messages results in flow management process crash

HIGH

7.5

CVSS Score

Published: January 15, 2026 at 08:19 PM UTC

Updated: June 17, 2026 at 10:19 AM UTC

1 product affected across 1 vendorJunos

Using Junos OS by Juniper Networks?

Get instant alerts when new vulnerabilities affect Junos OS - before attackers find them.

Real-time alertsTrack your software stackFree plan available

Start Free Sign In

Severity

HIGH7.5

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

v < 21.2v < 21.2R3-S1021.4 ≤ v < 21.4R3-S1222.4 ≤ v < 22.4R3-S823.2 ≤ v < 23.2R2-S523.4 ≤ v < 23.4R2-S624.2 ≤ v < 24.2R2-S324.4 ≤ v < 24.4R2-S125.2 ≤ v < 25.2R1-S1, 25.2R221.2 21.2 r1 21.2 r1-s1 21.2 r1-s2 21.2 r2 21.2 r2-s1 21.2 r2-s2 21.2 r3 21.2 r3-s1 21.2 r3-s2 21.2 r3-s3 21.2 r3-s4 21.2 r3-s5 21.2 r3-s6 21.2 r3-s7 21.2 r3-s8 21.2 r3-s9 21.4 21.4 r1 21.4 r1-s1 21.4 r1-s2 21.4 r2 21.4 r2-s1 21.4 r2-s2 21.4 r3 21.4 r3-s1 21.4 r3-s10 21.4 r3-s11 21.4 r3-s2 21.4 r3-s3 21.4 r3-s4 21.4 r3-s5 21.4 r3-s6 21.4 r3-s7 21.4 r3-s8 21.4 r3-s9 22.4 22.4 r1 22.4 r1-s1 22.4 r1-s2 22.4 r2 22.4 r2-s1 22.4 r2-s2 22.4 r3 22.4 r3-s1 22.4 r3-s2 22.4 r3-s3 22.4 r3-s4 22.4 r3-s5 22.4 r3-s6 22.4 r3-s7 23.2 23.2 r1 23.2 r1-s1 23.2 r1-s2 23.2 r2 23.2 r2-s1 23.2 r2-s2 23.2 r2-s3 23.2 r2-s4 23.4 23.4 r1 23.4 r1-s1 23.4 r1-s2 23.4 r2 23.4 r2-s1 23.4 r2-s2 23.4 r2-s3 23.4 r2-s4 23.4 r2-s5 24.2 24.2 r1 24.2 r1-s1 24.2 r1-s2 24.2 r2 24.2 r2-s1 24.2 r2-s2 24.4 24.4 r1 24.4 r1-s2 24.4 r1-s3 24.4 r2 25.2 25.2 r1 25.2 r2

Affected range stops below 21.2R3-S10, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.4R3-S12, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.4R3-S8, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R2-S5, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.4R2-S6, so it looks safe — our inference, not a vendor statement

Affected range stops below 24.2R2-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 24.4R2-S1, so it looks safe — our inference, not a vendor statement

Affected range stops below 25.2R1-S1, 25.2R2, so it looks safe — our inference, not a vendor statement

juniper-mx10004 (environment) · juniper-mx10008 (environment) · juniper-mx2008 (environment) · juniper-mx2010 (environment) · juniper-mx2020 (environment) · juniper-mx204 (environment) · juniper-mx240 (environment) · juniper-mx304 (environment) · juniper-mx480 (environment) · juniper-mx960 (environment) · juniper-srx1500 (environment) · juniper-srx1600 (environment) · juniper-srx2300 (environment) · juniper-srx300 (environment) · juniper-srx320 (environment) · juniper-srx340 (environment) · juniper-srx345 (environment) · juniper-srx380 (environment) · juniper-srx4100 (environment) · juniper-srx4120 (environment) · juniper-srx4200 (environment) · juniper-srx4300 (environment) · juniper-srx4600 (environment) · juniper-srx4700 (environment) · juniper-srx5400 (environment) · juniper-srx5600 (environment) · juniper-srx5800 (environment)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Vendor Advisory

Source: cverecord

https://supportportal.juniper.net/JSA106004

Vendor Advisory

Source: cverecord

https://kb.juniper.net/JSA106004

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHjuniper

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusANALYZED

CWE

CWE-835

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create account Sign in

Free plan, no card