Junos OS (SRX firewalls)
CVE-2026-57026: MX Series with SPC3, SRX Series: Processing of a specifically malformed SIP invite causes a flowd crash
An Improper Validation of Syntactic Correctness of Input vulnerability in the SIP plugin of Juniper Networks Junos OS on MX Series with SPC3 and SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).If the SIP ALG is enabled on an affected device, the processing of a malformed SIP invite packet will cause a flow processing daemon (flowd) crash and restart.
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 (SRX Series, MX Series with SPC3) 0 | 23.2R2-S7 or later |
| Junos OS (SRX Series, MX Series with SPC3) 23.4 | 23.4R2-S8 or later |
| Junos OS (SRX Series, MX Series with SPC3) 24.2 | 24.2R2-S5 or later |
| Junos OS (SRX Series, MX Series with SPC3) 24.4 | 24.4R2-S4 or later |
| Junos OS (SRX Series, MX Series with SPC3) 25.2 | 25.2R2 or later |
| Junos OS (SRX Series, MX Series with SPC3) 25.4 | 25.4R1-S2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
An Improper Validation of Syntactic Correctness of Input vulnerability in the SIP plugin of Juniper Networks Junos OS on MX Series with SPC3 and SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).If the SIP ALG is enabled on an affected device, the processing of a malformed SIP invite packet will cause a flow processing daemon (flowd) crash and restart. This leads to a complete service outage until the system has automatically recovered.
This issue affects Junos OS on MX Series with SPC3 and SRX Series:
- all versions before 23.2R2-S7,
- 23.4 versions before 23.4R2-S8,
- 24.2 versions before 24.2R2-S5,
- 24.4 versions before 24.4R2-S4,
- 25.2 versions before 25.2R2,
- 25.4 versions before 25.4R1-S2.
Am I affected?
To be affected the SIP ALG needs to be enabled, either implicitly / by default or by way of configuration. Please verify with:
user@host> show security alg status | match sip SIP : Enabled
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.