CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
AV:N/AC:M/Au:N/C:N/I:P/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
Percentile
31.8%
Revision | Date | Changes |
---|---|---|
1.0 | April 1st, 2022 | Initial Release |
The CVE-ID tracking this issue: CVE-2021-28504
CVSSv3.1 Base Score: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N)
Common Weakness Enumeration: CWE-284 Improper Access Control
This vulnerability is being tracked by BUG 614735
On affected platforms running Arista EOS, deny rules fail to get applied for packets of size higher than the configured maximum transmission unit (MTU), which results in packets of large size getting routed by the switch.
This issue was discovered internally and Arista is not aware of any malicious uses of this issue in customer networks.
The following products are affected by this vulnerability:
The following product versions and platforms are not affected by this vulnerability:
Arista EOS-based products:
Arista Wireless Access Points
CloudVision WiFi virtual appliance or physical appliance
CloudVision WiFi cloud service delivery
CloudVision Portal, virtual appliance or physical appliance
CloudVision as-a-Service
Arista 7130 Systems running MOS
Arista Converged Cloud Fabric and DANZ Monitoring Fabric (Formerly Big Switch Nodes for BCF and BMF)
Awake Security Platform
In order to be vulnerable to CVE-2021-28504 the following conditions must be all be met:
Routing should be enabled on the switch. To determine if routing is enabled on the switch,
switch# show running-config | include ip routing
ip routing
Layer3 interfaces must be active. To determine if L3 interfaces exist on the switch,
switch# show ip interface brief | exclude Management
Address
Interface IP Address Status Protocol MTU Owner
------------------- ---------------------- ------------ -------------------- ---------- -------
Vlan1000 unassigned up up 1500
Ingress data plane ACL should be applied to routed port / SVI. Run the following command to determine if “active on ingress” line has one or more L3 interfaces
switch# show ip access-lists deny summary
IPV4 ACL deny
Total rules configured: 1
Configured on Ingress: Et1/1,Vl1000
Active on Ingress: Et1/1,Vl1000
switch #show ip access-lists deny
IP Access List deny
1 permit tcp any eq bgp any
2 permit tcp any any eq bgp
3 permit udp any any eq 179
4 permit udp any eq 179 any
10 deny ip any any
There are no indicators in logs and syslogs.
If configurations above are all met then, there is a potential for packets with length greater than configured / default MTU to be fragmented and routed via control-plane.
To check CPU forwarding run _show cpu counters queue | nz_
. If _L3 Slow Path_
queue shows an unexpected increase in the rate of packets forwarded by the CPU then this may be an indication of the issue.
switch# show cpu counters queue | nz
-----------------------------------------------------------------------------------------------
SwitchcardCes1/0
-----------------------------------------------------------------------------------------------
Queue Counters/pkts Drops/pkts
-----------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
SwitchcardCes2/0
-----------------------------------------------------------------------------------------------
Queue Counters/pkts Drops/pkts
-----------------------------------------------------------------------------------------------
**L3 Slow Path** **100** 0
There is no mitigation / workaround for this issue.
The recommended resolution is to upgrade to a remediated software version at your earliest convenience. Arista recommends customers move to the latest version of each release that contains all the fixes listed below.
CVE-2021-28504 has been fixed in the following releases:
If you require further assistance, or if you have any further questions regarding this security notice, please contact the Arista Networks Technical Assistance Center (TAC) by one of the following methods:
By email: This email address is being protected from spambots. You need JavaScript enabled to view it.
By telephone: 408-547-5502 ; 866-476-0000
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
AV:N/AC:M/Au:N/C:N/I:P/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
Percentile
31.8%