CVE-2021-28511

Public Exploit
This advisory documents the impact of an internally found vulnerability in Arista EOS for security ACL bypass. The impact of this vulnerability is that the security ACL drop rule might be bypassed if a NAT ACL rule filter with permit action matches t ...

Description

This advisory documents the impact of an internally found vulnerability in Arista EOS for security ACL bypass. The impact of this vulnerability is that the security ACL drop rule might be bypassed if a NAT ACL rule filter with permit action matches the packet flow. This could allow a host with an IP address in a range that matches the range allowed by a NAT ACL and a range denied by a Security ACL to be forwarded incorrectly as it should have been denied by the Security ACL. This can enable an ACL bypass.

Remediation

Solution:

  • The recommended resolution is to upgrade to a remediated software version at your earliest convenience. The fixed versions for the currently supported release trains are as follows: 4.24.10 and later releases in the 4.24.x train 4.25.9 and later releases in the 4.25.x train 4.26.6 and later releases in the 4.26.x train 4.27.4 and later releases in the 4.27.x train 4.28.0 and later releases in the 4.28.x train

Workaround:

  • Configure a NAT “drop” ACL rule for each security ACL “drop” rule that should be applied to the interface that has NAT configured. This will prevent the packets from being translated at the expense of maintaining the configuration in two places.

Category

5.8
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.06%
Vendor Advisory arista.com
Affected: Arista Networks EOS
Published at:
Updated at:

References

Link Tags
https://www.arista.com/en/support/advisories-notices/security-advisory/15862-security-advisory-0078 vendor advisory mitigation exploit

Frequently Asked Questions

What is the severity of CVE-2021-28511?
CVE-2021-28511 has been scored as a medium severity vulnerability.
How to fix CVE-2021-28511?
To fix CVE-2021-28511: The recommended resolution is to upgrade to a remediated software version at your earliest convenience. The fixed versions for the currently supported release trains are as follows: 4.24.10 and later releases in the 4.24.x train 4.25.9 and later releases in the 4.25.x train 4.26.6 and later releases in the 4.26.x train 4.27.4 and later releases in the 4.27.x train 4.28.0 and later releases in the 4.28.x train
Is CVE-2021-28511 being actively exploited in the wild?
It is possible that CVE-2021-28511 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-28511?
CVE-2021-28511 affects Arista Networks EOS.
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