A Use After Free vulnerability in the Advanced Forwarding Toolkit (AFT) manager process (aftmand) of Juniper Networks Junos OS allows an unauthenticated networked attacker to cause a kernel crash due to intensive polling of Abstracted Fabric (AF) interface statistics and thereby a Denial of Service (DoS). Continued gathering of AF interface statistics will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on MX Series: 20.1 versions later than 20.1R1; 20.2 versions prior to 20.2R3-S5; 20.3 versions prior to 20.3R3-S4; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2; 21.2 versions prior to 21.2R2.
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Junos | Juniper | 20.1-r1-s1 (including) | 20.1-r1-s1 (including) |
| Junos | Juniper | 20.1-r1-s2 (including) | 20.1-r1-s2 (including) |
| Junos | Juniper | 20.1-r1-s3 (including) | 20.1-r1-s3 (including) |
| Junos | Juniper | 20.1-r1-s4 (including) | 20.1-r1-s4 (including) |
| Junos | Juniper | 20.1-r2 (including) | 20.1-r2 (including) |
| Junos | Juniper | 20.1-r2-s1 (including) | 20.1-r2-s1 (including) |
| Junos | Juniper | 20.1-r2-s2 (including) | 20.1-r2-s2 (including) |
| Junos | Juniper | 20.1-r3 (including) | 20.1-r3 (including) |
| Junos | Juniper | 20.1-r3-s1 (including) | 20.1-r3-s1 (including) |
| Junos | Juniper | 20.1-r3-s2 (including) | 20.1-r3-s2 (including) |
| Junos | Juniper | 20.1-r3-s3 (including) | 20.1-r3-s3 (including) |
| Junos | Juniper | 20.2 (including) | 20.2 (including) |
| Junos | Juniper | 20.2-r1 (including) | 20.2-r1 (including) |
| Junos | Juniper | 20.2-r1-s1 (including) | 20.2-r1-s1 (including) |
| Junos | Juniper | 20.2-r1-s2 (including) | 20.2-r1-s2 (including) |
| Junos | Juniper | 20.2-r1-s3 (including) | 20.2-r1-s3 (including) |
| Junos | Juniper | 20.2-r2 (including) | 20.2-r2 (including) |
| Junos | Juniper | 20.2-r2-s1 (including) | 20.2-r2-s1 (including) |
| Junos | Juniper | 20.2-r2-s2 (including) | 20.2-r2-s2 (including) |
| Junos | Juniper | 20.2-r2-s3 (including) | 20.2-r2-s3 (including) |
| Junos | Juniper | 20.2-r3 (including) | 20.2-r3 (including) |
| Junos | Juniper | 20.2-r3-s1 (including) | 20.2-r3-s1 (including) |
| Junos | Juniper | 20.2-r3-s2 (including) | 20.2-r3-s2 (including) |
| Junos | Juniper | 20.2-r3-s3 (including) | 20.2-r3-s3 (including) |
| Junos | Juniper | 20.2-r3-s4 (including) | 20.2-r3-s4 (including) |
| Junos | Juniper | 20.3 (including) | 20.3 (including) |
| Junos | Juniper | 20.3-r1 (including) | 20.3-r1 (including) |
| Junos | Juniper | 20.3-r1-s1 (including) | 20.3-r1-s1 (including) |
| Junos | Juniper | 20.3-r1-s2 (including) | 20.3-r1-s2 (including) |
| Junos | Juniper | 20.3-r2 (including) | 20.3-r2 (including) |
| Junos | Juniper | 20.3-r2-s1 (including) | 20.3-r2-s1 (including) |
| Junos | Juniper | 20.3-r3 (including) | 20.3-r3 (including) |
| Junos | Juniper | 20.3-r3-s1 (including) | 20.3-r3-s1 (including) |
| Junos | Juniper | 20.3-r3-s2 (including) | 20.3-r3-s2 (including) |
| Junos | Juniper | 20.3-r3-s3 (including) | 20.3-r3-s3 (including) |
| Junos | Juniper | 20.4 (including) | 20.4 (including) |
| 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 | 21.1 (including) | 21.1 (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 | 21.2 (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) |
The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:
In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.