How severe is CVE-2021-28511?

CVE-2021-28511 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-28511 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28511?

CVE-2021-28511 affects Arista Eos. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-28511?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-28511 published?

CVE-2021-28511 was published on 2022-08-05 and last updated on 2026-06-17.

CVE-2021-28511

CVE-2021-28511 is a medium-severity vulnerability in Arista Eos with a CVSS 3.x base score of 5.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-284.

Key facts

Severity: Medium (CVSS 3.x base score 5.8)
EPSS exploit prediction: 1% (45th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-284
Affected product: Arista Eos
Published: 2022-08-05
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-28511?: 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.
How severe is CVE-2021-28511?: CVE-2021-28511 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-28511 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28511?: CVE-2021-28511 affects Arista Eos. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-28511?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-28511 published?: CVE-2021-28511 was published on 2022-08-05 and last updated on 2026-06-17.

References

https://www.arista.com/en/support/advisories-notices/security-advisory/15862-security-advisory-0078

Affected products (1)

cpe:2.3:o:arista:eos:*:*:*:*:*:*:*:*

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