On PTX Series and QFX10k Series devices with the inline-jflow feature enabled, a use after free weakness in the Packet Forwarding Engine (PFE) microkernel architecture of Juniper Networks Junos OS may allow an attacker to cause a Denial of Service (DoS) condition whereby one or more Flexible PIC Concentrators (FPCs) may restart. As this is a race condition situation this issue become more likely to be hit when network instability occurs, such as but not limited to BGP/IGP reconvergences, and/or further likely to occur when more active traffic flows are occurring through the device. When this issue occurs, it will cause one or more FPCs to restart unexpectedly. During FPC restarts core files will be generated. While the core file is generated traffic will be disrupted. Sustained receipt of large traffic flows and reconvergence-like situations may sustain the Denial of Service (DoS) situation. This issue affects: Juniper Networks Junos OS: 18.1 version 18.1R2 and later versions prior to 18.1R3-S10 on PTX Series, QFX10K Series.
The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Junos | Juniper | 18.1-r2 (including) | 18.1-r2 (including) |
| Junos | Juniper | 18.1-r2-s1 (including) | 18.1-r2-s1 (including) |
| Junos | Juniper | 18.1-r2-s2 (including) | 18.1-r2-s2 (including) |
| Junos | Juniper | 18.1-r2-s4 (including) | 18.1-r2-s4 (including) |
| Junos | Juniper | 18.1-r3 (including) | 18.1-r3 (including) |
| Junos | Juniper | 18.1-r3-s1 (including) | 18.1-r3-s1 (including) |
| Junos | Juniper | 18.1-r3-s2 (including) | 18.1-r3-s2 (including) |
| Junos | Juniper | 18.1-r3-s3 (including) | 18.1-r3-s3 (including) |
| Junos | Juniper | 18.1-r3-s4 (including) | 18.1-r3-s4 (including) |
| Junos | Juniper | 18.1-r3-s5 (including) | 18.1-r3-s5 (including) |
| Junos | Juniper | 18.1-r3-s6 (including) | 18.1-r3-s6 (including) |
| Junos | Juniper | 18.1-r3-s7 (including) | 18.1-r3-s7 (including) |
| Junos | Juniper | 18.1-r3-s8 (including) | 18.1-r3-s8 (including) |
| Junos | Juniper | 18.1-r3-s9 (including) | 18.1-r3-s9 (including) |
This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider. A race condition occurs within concurrent environments, and is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:
A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. Programmers may assume that certain code sequences execute too quickly to be affected by an interfering code sequence; when they are not, this violates atomicity. For example, the single “x++” statement may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read (the original value of x), followed by a computation (x+1), followed by a write (save the result to x). The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.