An Improper Check for Unusual or Exceptional Conditions vulnerability in the processing of specific IPv6 packets on certain EX Series devices may lead to exhaustion of DMA memory causing a Denial of Service (DoS). Over time, exploitation of this vulnerability may cause traffic to stop being forwarded, or a crash of the fxpc process. An indication of the issue occurring may be observed through the following log messages: Sep 13 17:14:59 hostname : %PFE-3: fpc0 (buf alloc) failed allocating packet buffer Sep 13 17:14:59 hostname : %PFE-7: fpc0 brcm_pkt_buf_alloc:393 (buf alloc) failed allocating packet buffer When Packet DMA heap utilization reaches 99%, the system will become unstable. Packet DMA heap utilization can be monitored using the command: user@junos# request pfe execute target fpc0 timeout 30 command “show heap” ID Base Total(b) Free(b) Used(b) % Name — ————— —————– —————– —————– —– —————– 0 213301a8 536870488 387228840 149641648 27 Kernel 1 91800000 8388608 3735120 4653488 55 DMA 2 92000000 75497472 74452192 1045280 1 PKT DMA DESC 3 d330000 335544320 257091400 78452920 23 Bcm_sdk 4 96800000 184549376 2408 184546968 99 Packet DMA <<<< 5 903fffe0 20971504 20971504 0 0 Blob This issue affects: Juniper Networks Junos OS 18.4 versions prior to 18.4R2-S10, 18.4R3-S10 on EX2300 Series, EX2300-MP Series, EX3400 Series; 19.1 versions prior to 19.1R3-S7 on EX2300 Series, EX2300-MP Series, EX3400 Series; 19.2 versions prior to 19.2R1-S8, 19.2R3-S4 on EX2300 Series, EX2300-MP Series, EX3400 Series; 19.3 versions prior to 19.3R3-S5 on EX2300 Series, EX2300-MP Series, EX3400 Series; 19.4 versions prior to 19.4R3-S7 on EX2300 Series, EX2300-MP Series, EX3400 Series; 20.1 versions prior to 20.1R3-S3 on EX2300 Series, EX2300-MP Series, EX3400 Series; 20.2 versions prior to 20.2R3-S3 on EX2300 Series, EX2300-MP Series, EX3400 Series; 20.3 versions prior to 20.3R3-S2 on EX2300 Series, EX2300-MP Series, EX3400 Series; 20.4 versions prior to 20.4R3-S1 on EX2300 Series, EX2300-MP Series, EX3400 Series; 21.1 versions prior to 21.1R2-S2, 21.1R3 on EX2300 Series, EX2300-MP Series, EX3400 Series; 21.2 versions prior to 21.2R1-S2, 21.2R2 on EX2300 Series, EX2300-MP Series, EX3400 Series; 21.3 versions prior to 21.3R1-S1, 21.3R2 on EX2300 Series, EX2300-MP Series, EX3400 Series.