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   JSA11118 - 2021-04 Security Bulletin: Junos OS: ACX5448, ACX710: BFD
        sessions might flap due to high rate of transit ARP packets
                               15 April 2021


        AusCERT Security Bulletin Summary

Product:           Junos OS: ACX5448
                   Junos OS: ACX710
Publisher:         Juniper Networks
Operating System:  Juniper
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-0216  

Original Bulletin: 

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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
Last Updated: 14 Apr 2021
Version     : 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:

  o 18.2 versions prior to 18.2R3-S8 on ACX5448;
  o 18.3 versions prior to 18.3R3-S5 on ACX5448;
  o 18.4 versions prior to 18.4R1-S6, 18.4R3-S7 on ACX5448;
  o 19.1 versions prior to 19.1R3-S5 on ACX5448;
  o 19.2 versions prior to 19.2R2, 19.2R3 on ACX5448;
  o 19.3 versions prior to 19.3R3 on ACX5448;
  o 19.4 versions prior to 19.4R3 on ACX5448;
  o 20.1 versions prior to 20.1R2 on ACX5448;
  o 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 https://
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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