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2021-04 Security Bulletin: Junos OS: ACX5448, ACX710: BFD sessions might flap due to high rate of transit ARP packets (CVE-2021-0216)



Article ID: JSA11118 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 1.0
Product Affected:
This issue affects Junos OS 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2. Affected platforms: ACX5448, ACX710

A vulnerability in Juniper Networks Junos OS running on the ACX5448 and ACX710 platforms may cause BFD sessions to flap when a high rate of transit ARP packets are received. This, in turn, may impact routing protocols and network stability, leading to a Denial of Service (DoS) condition.

When a high rate of transit ARP packets are exceptioned to the CPU and BFD flaps, the following log messages may be seen:

bfdd[15864]: BFDD_STATE_UP_TO_DOWN: BFD Session (IFL 232) state Up -> Down LD/RD(17/19) Up time:11:38:17 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
bfdd[15864]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 17, new state: down, interface: irb.998, peer addr:
rpd[15839]: RPD_ISIS_ADJDOWN: IS-IS lost L2 adjacency to peer on irb.998, reason: BFD Session Down
bfdd[15864]: BFDD_TRAP_SHOP_STATE_UP: local discriminator: 17, new state: up, interface: irb.998, peer addr:

This issue only affects the ACX5448 Series and ACX710 Series routers. No other products or platforms are affected by this vulnerability.

This issue affects Juniper Networks Junos OS:

  • 18.2 versions prior to 18.2R3-S8 on ACX5448;
  • 18.3 versions prior to 18.3R3-S5 on ACX5448;
  • 18.4 versions prior to 18.4R1-S6, 18.4R3-S7 on ACX5448;
  • 19.1 versions prior to 19.1R3-S5 on ACX5448;
  • 19.2 versions prior to 19.2R2, 19.2R3 on ACX5448;
  • 19.3 versions prior to 19.3R3 on ACX5448;
  • 19.4 versions prior to 19.4R3 on ACX5448;
  • 20.1 versions prior to 20.1R2 on ACX5448;
  • 20.2 versions prior to 20.2R2 on ACX5448 and ACX710.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2021-0216.


The following software releases have been updated to resolve this specific issue: Junos OS 18.2R3-S8, 18.3R3-S5, 18.4R1-S6, 18.4R3-S7, 19.1R3-S5, 19.2R2, 19.2R3, 19.3R3, 19.4R3, 20.1R2, 20.2R2, 20.3R1, and all subsequent releases.

This issue is being tracked as 1477261.

There are no viable workarounds for this issue.
Software releases or updates are available for download at
Modification History:
2021-04-14: Initial Publication.
CVSS Score:
6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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