CVE-2021-28511: arista networks eos Improper Access Control
Vulnerability summary
CVE-2021-28511 is a medium (CVSS 6.5) Improper Access Control vulnerability in arista networks eos. EPSS estimates a 0.58% chance of exploitation in the next 30 days, higher than 46.6% of scored vulnerabilities. 1 public exploit is recorded.
Timeline
- 05-08-2022PublishedVulnerability first disclosed.
- 02-06-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
2 scores · 2 sources · 1 version- CVE.orgCNA5.8MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:NDiffers
EPSS trend
Probability
0.58%
Chance of exploitation in the next 30 days
Percentile
47%
Versus all other CVEs
30-day change
+0.01 pp
From 0.57% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundExploit Reference (arista.com)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Arista1 product
- eos≤ 4.24.9 | ≥ 4.25.0, ≤ 4.25.8 | ≥ 4.26.0, ≤ 4.26.5 | ≥ 4.27.0, ≤ 4.27.3
Arista networks1 product
- eos≥ 4.24.0, ≤ 4.24.9 | ≥ 4.25.0, ≤ 4.25.8 | ≥ 4.26.0, ≤ 4.26.5 | ≥ 4.27.0, ≤ 4.27.3
2 vendors · 2 products
References
1 links- www.arista.com/en/support/advisories-notices/security-advisory/15862-security-advisory-0078X Refsource MISCExploitMitigationVendor Advisory