A Use After Free vulnerability in the Layer 2 Address Learning Manager (l2alm) of Juniper Networks Junos OS on QFX Series allows an adjacent attacker to cause the Packet Forwarding Engine to crash and restart, leading to a Denial of Service (DoS). The PFE may crash when a lot of MAC learning and aging happens, but due to a Race Condition (Concurrent Execution using Shared Resource with Improper Synchronization) that is outside the attackers direct control. This issue affects: Juniper Networks Junos OS versions prior to 19.4R3-S10 on QFX Series; 20.2 versions prior to 20.2R3-S7 on QFX Series; 20.3 versions prior to 20.3R3-S6 on QFX Series; 20.4 versions prior to 20.4R3-S5 on QFX Series; 21.1 versions prior to 21.1R3-S4 on QFX Series; 21.2 versions prior to 21.2R3-S3 on QFX Series; 21.3 versions prior to 21.3R3-S3 on QFX Series; 21.4 versions prior to 21.4R3 on QFX Series; 22.1 versions prior to 22.1R3 on QFX Series; 22.2 versions prior to 22.2R2 on QFX Series.
The product contains a concurrent code sequence that 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 operating concurrently.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| 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 | 20.2-r3-s5 (including) | 20.2-r3-s5 (including) |
| Junos | Juniper | 20.2-r3-s6 (including) | 20.2-r3-s6 (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 | 20.3-r3-s4 (including) | 20.3-r3-s4 (including) |
| Junos | Juniper | 20.3-r3-s5 (including) | 20.3-r3-s5 (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 | 20.4-r3 (including) | 20.4-r3 (including) |
| Junos | Juniper | 20.4-r3-s1 (including) | 20.4-r3-s1 (including) |
| Junos | Juniper | 20.4-r3-s2 (including) | 20.4-r3-s2 (including) |
| Junos | Juniper | 20.4-r3-s3 (including) | 20.4-r3-s3 (including) |
| Junos | Juniper | 20.4-r3-s4 (including) | 20.4-r3-s4 (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 | 21.1-r2 (including) | 21.1-r2 (including) |
| Junos | Juniper | 21.1-r2-s1 (including) | 21.1-r2-s1 (including) |
| Junos | Juniper | 21.1-r2-s2 (including) | 21.1-r2-s2 (including) |
| Junos | Juniper | 21.1-r3 (including) | 21.1-r3 (including) |
| Junos | Juniper | 21.1-r3-s1 (including) | 21.1-r3-s1 (including) |
| Junos | Juniper | 21.1-r3-s2 (including) | 21.1-r3-s2 (including) |
| Junos | Juniper | 21.1-r3-s3 (including) | 21.1-r3-s3 (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) |
| 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 | 21.3 (including) | 21.3 (including) |
| Junos | Juniper | 21.3-r1 (including) | 21.3-r1 (including) |
| Junos | Juniper | 21.3-r1-s1 (including) | 21.3-r1-s1 (including) |
| Junos | Juniper | 21.3-r1-s2 (including) | 21.3-r1-s2 (including) |
| Junos | Juniper | 21.3-r2 (including) | 21.3-r2 (including) |
| Junos | Juniper | 21.3-r2-s1 (including) | 21.3-r2-s1 (including) |
| Junos | Juniper | 21.3-r2-s2 (including) | 21.3-r2-s2 (including) |
| Junos | Juniper | 21.3-r3 (including) | 21.3-r3 (including) |
| Junos | Juniper | 21.3-r3-s1 (including) | 21.3-r3-s1 (including) |
| Junos | Juniper | 21.3-r3-s2 (including) | 21.3-r3-s2 (including) |
| Junos | Juniper | 21.4 (including) | 21.4 (including) |
| Junos | Juniper | 21.4-r1 (including) | 21.4-r1 (including) |
| Junos | Juniper | 21.4-r1-s1 (including) | 21.4-r1-s1 (including) |
| Junos | Juniper | 21.4-r1-s2 (including) | 21.4-r1-s2 (including) |
| Junos | Juniper | 21.4-r2 (including) | 21.4-r2 (including) |
| Junos | Juniper | 21.4-r2-s1 (including) | 21.4-r2-s1 (including) |
| Junos | Juniper | 21.4-r2-s2 (including) | 21.4-r2-s2 (including) |
| Junos | Juniper | 22.1-r1 (including) | 22.1-r1 (including) |
| Junos | Juniper | 22.1-r1-s1 (including) | 22.1-r1-s1 (including) |
| Junos | Juniper | 22.1-r1-s2 (including) | 22.1-r1-s2 (including) |
| Junos | Juniper | 22.1-r2 (including) | 22.1-r2 (including) |
| Junos | Juniper | 22.1-r2-s1 (including) | 22.1-r2-s1 (including) |
| Junos | Juniper | 22.2-r1 (including) | 22.2-r1 (including) |
| Junos | Juniper | 22.2-r1-s1 (including) | 22.2-r1-s1 (including) |
| Junos | Juniper | 22.2-r1-s2 (including) | 22.2-r1-s2 (including) |
| Junos | Juniper | 22.3-r1 (including) | 22.3-r1 (including) |
| Junos | Juniper | 22.4-r1 (including) | 22.4-r1 (including) |
A race condition occurs within concurrent environments, and it 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. 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.