Security readout for executives and security teams
Plain-English summary
Certain Arista EOS systems may mishandle outbound access-control rules when MACsec and egress ACLs are enabled on the same interface. Traffic that should be blocked might pass, or traffic that should pass might be denied. The issue is configuration-specific, not a broad default exposure.
Executive priority
Treat this as a moderate network-control risk. Prioritize environments using Arista MACsec with egress ACLs on sensitive links, because intended outbound segmentation or filtering may not hold reliably.
Technical view
CVE-2024-27891 is a CWE-284 access-control enforcement flaw in Arista EOS. On affected platforms and versions, egress ACL policies may not be enforced correctly on interfaces also using MACsec, causing incorrect allow or deny decisions for egress packets. CVSS v4.0 score is 6.9.
Likely exposure
Exposure appears limited to affected Arista EOS versions 4.27.2F through 4.32.0 on affected platforms where MACsec and egress ACLs are configured together on the same ports.
Exploitation context
The source bundle does not identify active exploitation, and the CVE is not marked KEV. Available evidence describes a policy-enforcement failure, not a public exploit path or weaponized technique.
Researcher notes
Evidence is limited to the CVE record and Arista advisory reference. The affected condition is specific: MACsec plus egress ACLs on the same interface. Do not assume impact on ingress ACLs, non-MACsec ports, or other Arista products without vendor confirmation.
Mitigation direction
- Check Arista advisory 0102 for fixed EOS releases or vendor workarounds.
- Inventory Arista EOS versions against the affected version list.
- Identify interfaces using both MACsec and egress ACLs.
- Reduce reliance on affected egress ACL paths until vendor guidance is applied.
- Prioritize changes for links carrying sensitive or regulated traffic.
Validation and detection
- Confirm whether deployed EOS versions match the affected list.
- Audit interface configurations for MACsec and egress ACL coexistence.
- Review whether egress ACLs enforce critical segmentation or data-loss controls.
- Validate policy behavior in a controlled test or maintenance window.
- Track Arista advisory updates for remediation details.
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-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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-2024-27891 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
- Medium
- CVSS
- 6.9 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
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
2 official scoresWe 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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N——AristaCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N3.91.4AristaVulnerability scoring details
Base CVSS 4.0 score
6.9MediumVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.arista.com/en/support/advisories-notices/security-advisory/19908-security-advisory-0102CVE reference, Arista
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.
Improper Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.