Authentication bypass in Arista EOS
Priority MEDIUM 43CWE-305Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-287.
Summary
The impact of this vulnerability is that Arista's EOS eAPI may skip re-evaluating user credentials when certificate based authentication is used, which allows remote attackers to access the device via eAPI.
Why it matters now
EPSS 0.00735 54th percentileScored 2026-11-08
Fix Fixed Arista EOS (Arista Networks): EOS-4.23.10, EOS-4.24.8, EOS-4.25.6 +1
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Arista | Arista EOS | EOS-4.23 to before EOS-4.23.10; EOS-4.24 to before EOS-4.24.8; EOS-4.25 to before EOS-4.25.6; EOS-4.26 to before EOS-4.26.3 | EOS-4.23.10, EOS-4.24.8, EOS-4.25.6, EOS-4.26.3 | Patch available | CNA |
- Arista EOS VendorArista Affected EOS-4.23 to before EOS-4.23.10; EOS-4.24 to before EOS-4.24.8; EOS-4.25 to before EOS-4.25.6; EOS-4.26 to before EOS-4.26.3 Fixed in EOS-4.23.10, EOS-4.24.8, EOS-4.25.6, EOS-4.26.3 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:arista:eos:*:*:*:*:*:*:*:* | 4.22 – 4.22.9m; 4.23 – 4.23.9; 4.24 – 4.24.7; 4.25 – 4.25.5; 4.26 – 4.26.2 | Vulnerable | Arista |
- cpe:2.3:o:arista:eos:*:*:*:*:*:*:*:* Versions 4.22 – 4.22.9m; 4.23 – 4.23.9; 4.24 – 4.24.7; 4.25 – 4.25.5; 4.26 – 4.26.2 Vulnerable ·Arista
Remediation
- Fix · CNA Arista EOS (Arista Networks) Fixed in EOS-4.23.10, EOS-4.24.8, EOS-4.25.6, EOS-4.26.3
Timeline
- 2026-10-02 Threatist record created from CVE-2021-28503
- 2026-10-03 Alias added: GHSA-mvw4-rrm9-fqfc
References
More Arista Eos vulnerabilities
- TI-2014-05975 GNU Bash through 4.3 bash43-025 processes trailing strings after certain malformed… KEVCVSS 3.1CRITICAL 9.8
- TI-2014-05157 GNU Bash through 4.3 processes trailing strings after function definitions in the values… KEVCVSS 3.1CRITICAL 9.8
- TI-2026-06569 Arista EOS Unexpected Tunnel Protocol Decapsulation and Forwarding Bypass KEVCVSS 4.0MEDIUM 6.9
- TI-2017-10594 Heap-based buffer overflow in dnsmasq before 2.78 allows remote attackers to cause a… CVSS 3.1CRITICAL 9.8
- TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
- TI-2020-08209 utility.c in telnetd in netkit telnet through 0.17 allows remote attackers to execute… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2021-28503 · CVE Program
- CVE-2021-28503 · NVD
- FIRST EPSS
- GHSA-mvw4-rrm9-fqfc · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences