Security readout for executives and security teams
Plain-English summary
This issue affects Arista EOS eAPI when certificate-based authentication is used. In affected releases, EOS may fail to re-check user credentials, letting a remote attacker access the device through eAPI. The business risk is unauthorized change or disruption of network infrastructure, not data theft according to the supplied CVSS impact.
Executive priority
Treat this as a high-priority network infrastructure remediation if affected Arista devices expose eAPI. Prioritize internet-facing or broadly reachable management interfaces first, then complete version and configuration validation across the fleet.
Technical view
CVE-2021-28503 is an Arista EOS authentication weakness in eAPI certificate-based authentication. Affected EOS 4.23, 4.24, 4.25, and 4.26 releases may skip credential re-evaluation, allowing unauthenticated remote eAPI access. CVSS 3.1 is 7.4: network attack vector, high complexity, no privileges, no user interaction, high integrity and availability impact.
Likely exposure
Exposure is most likely where Arista EOS 4.23 through 4.26 devices have eAPI enabled, use certificate-based authentication, and are reachable from untrusted networks or broad internal segments. The source bundle does not state default eAPI exposure or all fixed releases.
Exploitation context
The supplied data does not show known active exploitation, and the CVE is not listed as KEV. Exploitation is described as remote but high complexity, with potential access through eAPI and high integrity and availability impact.
Researcher notes
The source bundle identifies CWE-305 and describes credential re-evaluation being skipped during certificate-based eAPI authentication. It does not provide exploit details, default configuration state, or complete remediation text. Avoid assuming exposure without confirming eAPI, certificate-auth use, and EOS release.
Mitigation direction
- Review Arista Security Advisory 0072 for fixed releases and vendor-supported mitigations.
- Upgrade affected EOS 4.23 through 4.26 systems per Arista guidance.
- Restrict eAPI access to trusted management networks only.
- Disable eAPI where it is not operationally required.
- Review certificate-based authentication configuration on affected devices.
- Increase monitoring for unexpected eAPI sessions or configuration changes.
Validation and detection
- Inventory Arista EOS devices and record exact running versions.
- Identify systems running EOS 4.23, 4.24, 4.25, or 4.26.
- Confirm whether eAPI is enabled on each affected device.
- Confirm whether certificate-based authentication is used with eAPI.
- Check management-plane reachability to eAPI from untrusted networks.
- Review logs for unexpected eAPI access or configuration activity.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-305: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-28503 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H2.25.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.arista.com/en/support/advisories-notices/security-advisories/13605-security-advisory-0072CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Authentication Bypass by Primary Weakness
Authentication Bypass by Primary Weakness represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.