An Improper Validation of Syntactic Correctness of Input vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to cause Denial of Service (DoS).
On all Junos OS MX Series and SRX Series platforms, when SIP ALG is enabled, and a specific SIP packet is received and processed, NAT IP allocation fails for genuine traffic, which causes Denial of Service (DoS). Continuous receipt of this specific SIP ALG packet will cause a sustained DoS condition.
NAT IP usage can be monitored by running the following command.
user@srx> show security nat resource-usage source-pool <source_pool_name>
Pool name: source_pool_name .. Address Factor-index Port-range Used Avail Total Usage X.X.X.X 0 Single Ports 50258 52342 62464 96% ««<
Juniper Networks Junos OS on MX Series and SRX Series
The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Junos | Juniper | 21.2 (including) | 21.2 (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 | 21.2-r1-s2 (including) | 21.2-r1-s2 (including) |
| Junos | Juniper | 21.2-r2 (including) | 21.2-r2 (including) |
| Junos | Juniper | 21.2-r2-s1 (including) | 21.2-r2-s1 (including) |
| Junos | Juniper | 21.2-r2-s2 (including) | 21.2-r2-s2 (including) |
| Junos | Juniper | 21.2-r3 (including) | 21.2-r3 (including) |
| Junos | Juniper | 21.2-r3-s1 (including) | 21.2-r3-s1 (including) |
| Junos | Juniper | 21.2-r3-s2 (including) | 21.2-r3-s2 (including) |
| Junos | Juniper | 21.2-r3-s3 (including) | 21.2-r3-s3 (including) |
| Junos | Juniper | 21.2-r3-s4 (including) | 21.2-r3-s4 (including) |
| Junos | Juniper | 21.2-r3-s5 (including) | 21.2-r3-s5 (including) |
Often, complex inputs are expected to follow a particular syntax, which is either assumed by the input itself, or declared within metadata such as headers. The syntax could be for data exchange formats, markup languages, or even programming languages. When untrusted input is not properly validated for the expected syntax, attackers could cause parsing failures, trigger unexpected errors, or expose latent vulnerabilities that might not be directly exploitable if the input had conformed to the syntax.