Junos OS (SRX firewalls)
CVE-2024-39551: SRX Series and MX Series with SPC3 and MS-MPC/MIC: Receipt of specific packets in H.323 ALG causes traffic drop
An Uncontrolled Resource Consumption vulnerability in the H.323 ALG (Application Layer Gateway) of Juniper Networks Junos OS on SRX Series and MX Series with SPC3 and MS-MPC/MIC, allows an unauthenticated network-based attacker to send specific packets causing traffic loss leading to 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 (SRX Series, MX Series) 20.4 | 20.4R3-S10 or later |
| Junos OS (SRX Series, MX Series) 21.2 | 21.2R3-S6 or later |
| Junos OS (SRX Series, MX Series) 21.3 | 21.3R3-S5 or later |
| Junos OS (SRX Series, MX Series) 21.4 | 21.4R3-S6 or later |
| Junos OS (SRX Series, MX Series) 22.1 | 22.1R3-S4 or later |
| Junos OS (SRX Series, MX Series) 22.2 | 22.2R3-S2 or later |
| Junos OS (SRX Series, MX Series) 22.3 | 22.3R3-S1 or later |
| Junos OS (SRX Series, MX Series) 22.4 | 22.4R3 or later |
| Junos OS (SRX Series, MX Series) 23.2 | 23.2R2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
An Uncontrolled Resource Consumption vulnerability in the H.323 ALG (Application Layer Gateway) of Juniper Networks Junos OS on SRX Series and MX Series with SPC3 and MS-MPC/MIC, allows an unauthenticated network-based attacker to send specific packets causing traffic loss leading to Denial of Service (DoS).
Continued receipt and processing of these specific packets will sustain the Denial of Service condition.
The memory usage can be monitored using the below command.
user@host> show usp memory segment sha data objcache jsf This issue affects SRX Series and MX Series with SPC3 and MS-MPC/MIC:
- 20.4 before 20.4R3-S10,
- 21.2 before 21.2R3-S6,
- 21.3 before 21.3R3-S5,
- 21.4 before 21.4R3-S6,
- 22.1 before 22.1R3-S4,
- 22.2 before 22.2R3-S2,
- 22.3 before 22.3R3-S1,
- 22.4 before 22.4R3,
- 23.2 before 23.2R2.
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 with:
user@host> show security alg status | match sip SIP : Enabled Please verify on MX whether the following is configured:
user@host> show security alg status | match sip SIP : Enabled [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.
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.