CVE-2026-21905
published 2026-01-15CVE-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…
PriorityP347high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.37%
28.9th percentile
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
20 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| juniper | junos | < 21.2 | 21.2 |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos | — | — |
| juniper | junos_os | — | — |
| juniper | mx_series | — | — |
| juniper | srx_series | — | — |
| juniper_networks | junos_os | < 21.2R3-S10 | 21.2R3-S10 |
| juniper_networks | junos_os | >= 21.4 < 21.4R3-S12 | 21.4R3-S12 |
| juniper_networks | junos_os | >= 22.4 < 22.4R3-S8 | 22.4R3-S8 |
| juniper_networks | junos_os | >= 23.2 < 23.2R2-S5 | 23.2R2-S5 |
| juniper_networks | junos_os | >= 23.4 < 23.4R2-S6 | 23.4R2-S6 |
| juniper_networks | junos_os | >= 24.2 < 24.2R2-S3 | 24.2R2-S3 |
| juniper_networks | junos_os | >= 24.4 < 24.4R2-S1 | 24.4R2-S1 |
| juniper_networks | junos_os | >= 25.2 < 25.2R1-S1, 25.2R2 | 25.2R1-S1, 25.2R2 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv4.08.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:M/U:Amber
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Juniper
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
vendor_juniper·2026-01-15·CVSS 7.5
CVE-2026-21905 [HIGH] CWE-835 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
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 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
GHSA
GHSA-qxmf-m5mx-7vx7: A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX
ghsa_unreviewed·2026-01-15
CVE-2026-21905 [HIGH] CWE-835 GHSA-qxmf-m5mx-7vx7: A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX
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 iss
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2026-01-15
Published