Junos OS: MX Series: Decapsulation of specific GRE packets leads to PFE reset

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).When processing a high rate of specific GRE traffic destined to the device, the respective PFE will hang causing traffic forwarding to stop.

When this issue occurs the following logs can be observed:

<fpc #> MQSS(0): LI-3: Received a parcel with more than 512B accompanying data
CHASSISD_FPC_ASIC_ERROR: ASIC Error detected <...>

This issue affects Junos OS:

* all versions before 21.2R3-S9,
* 21.4 versions before 21.4R3-S8,
* 22.2 versions before 22.2R3-S4,
* 22.4 versions before 22.4R3-S5,
* 23.2 versions before 23.2R2-S2,
* 23.4 versions before 23.4R2.