An Improper Locking vulnerability in the SIP ALG of Juniper Networks Junos OS on MX Series and SRX Series allows an unauthenticated networked attacker to cause a flowprocessing daemon (flowd) crash and thereby a Denial of Service (DoS). Continued receipt of these specific packets will cause a sustained Denial of Service condition. This issue can occur in a scenario where the SIP ALG is enabled and specific SIP messages are being processed simultaneously. This issue affects: Juniper Networks Junos OS on MX Series and SRX Series 20.4 versions prior to 20.4R3-S1; 21.1 versions prior to 21.1R2-S2, 21.1R3; 21.2 versions prior to 21.2R1-S2, 21.2R2; 21.3 versions prior to 21.3R1-S1, 21.3R2. This issue does not affect Juniper Networks Junos OS versions prior to 20.4R1.
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Junos | Juniper | 20.4-r1 (including) | 20.4-r1 (including) |
| Junos | Juniper | 20.4-r1-s1 (including) | 20.4-r1-s1 (including) |
| Junos | Juniper | 20.4-r2 (including) | 20.4-r2 (including) |
| Junos | Juniper | 20.4-r2-s1 (including) | 20.4-r2-s1 (including) |
| Junos | Juniper | 20.4-r2-s2 (including) | 20.4-r2-s2 (including) |
| Junos | Juniper | 20.4-r3 (including) | 20.4-r3 (including) |
| Junos | Juniper | 21.1-r1 (including) | 21.1-r1 (including) |
| Junos | Juniper | 21.1-r1-s1 (including) | 21.1-r1-s1 (including) |
| Junos | Juniper | 21.1-r2 (including) | 21.1-r2 (including) |
| Junos | Juniper | 21.1-r2-s1 (including) | 21.1-r2-s1 (including) |
| Junos | Juniper | 21.2-r1 (including) | 21.2-r1 (including) |
| Junos | Juniper | 21.2-r1-s1 (including) | 21.2-r1-s1 (including) |
| Junos | Juniper | 21.3-r1 (including) | 21.3-r1 (including) |
Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.