Junos OS (SRX firewalls)
CVE-2025-30656: MX Series, SRX Series: Processing of specific SIP INVITE messages by the SIP ALG will lead to an FPC crash
An Improper Handling of Additional Special Element vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MS-MPC, MS-MIC and SPC3, and SRX Series, allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS (MX Series, SRX Series) 0 | 21.2R3-S9 or later |
| Junos OS (MX Series, SRX Series) 21.4 | 21.4R3-S10 or later |
| Junos OS (MX Series, SRX Series) 22.2 | 22.2R3-S6 or later |
| Junos OS (MX Series, SRX Series) 22.4 | 22.4R3-S5 or later |
| Junos OS (MX Series, SRX Series) 23.2 | 23.2R2-S3 or later |
| Junos OS (MX Series, SRX Series) 23.4 | 23.4R2-S3 or later |
| Junos OS (MX Series, SRX Series) 24.2 | 24.2R1-S2, 24.2R2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
An Improper Handling of Additional Special Element vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MS-MPC, MS-MIC and SPC3, and SRX Series, allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).
If the SIP ALG processes specifically formatted SIP invites, a memory corruption will occur which will lead to a crash of the FPC processing these packets. Although the system will automatically recover with the restart of the FPC, subsequent SIP invites will cause the crash again and lead to a sustained DoS.
This issue affects Junos OS on MX Series and SRX Series:
- all versions before 21.2R3-S9,
- 21.4 versions before 21.4R3-S10,
- 22.2 versions before 22.2R3-S6,
- 22.4 versions before 22.4R3-S5,
- 23.2 versions before 23.2R2-S3,
- 23.4 versions before 23.4R2-S3,
- 24.2 versions before 24.2R1-S2, 24.2R2.
Am I affected?
To be affected the SIP ALG needs to be enabled, either implicitly / by default or by way of configuration. Please verify on SRX, and MX with SPC3 with:
user@host> show security alg status | match sip SIP : Enabled
Please verify on MX whether the following is configured:
[ services ... rule <rule-name> (term <term-name> ) from/match application/application-set <name> ] where either
a. name = junos-sip or an application or application-set refers to SIP:
b. [ applications application <name> application-protocol sip ] or c. [ applications application-set <name> application junos-sip ]
Workarounds
There are no known workarounds for this issue.
To reduce the risk of exploitation customers not requiring the SIP ALG functionality could explicitly disable it (in case it's by default enabled) by configuring:
[ security alg sip disable
]
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.