CVE-2024-27891
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOn affected platforms running Arista EOS with MACsec and egress ACLs configured on the same interfaces, the ACL policies may not be enforced for packets egressing on those ports. This can cause outgoing packets to incorrectly be allowed or denied.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceOn Arista EOS platforms, when MACsec and egress ACLs are both configured on the same interfaces, the egress ACL policies fail to be properly enforced for outgoing packets. This can result in traffic being incorrectly allowed or denied based on ACL rules that are not being applied.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Arista EOS is in useRun 'show version' or check the device prompt to confirm the device runs Arista EOS softwareAffected if Device is not running Arista EOS (not affected)
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Identify interfaces with MACsec enabledRun 'show macsec interface' or 'show running-config | include macsec' to list interfaces where MACsec is configuredAffected if No interfaces have MACsec enabled (not affected)
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Identify interfaces with egress ACLs appliedRun 'show ip access-lists' and 'show ipv6 access-lists' to review ACL configurations, then check interface configs with 'show running-config interface' to identify which interfaces have egress ACLs applied (look for 'ip access-group ... out' or 'ipv6 access-group ... out')Affected if No interfaces have egress ACLs applied (not affected)
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Check for interface overlap between MACsec and egress ACLsCross-reference the interfaces identified in step 2 and step 3 to see if any interface appears in both listsAffected if The same interface has both MACsec enabled and an egress ACL applied (AFFECTED)
A user is affected if any interface in their environment has both MACsec and an egress ACL configured simultaneously, regardless of the EOS version.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataAudit all interfaces configured with both MACsec and egress ACLs, verify traffic filtering is functioning as intended, and consider relocating egress ACLs to separate interfaces or implementing alternative filtering until patches are applied.
- Consultation4.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,488.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2024-27891 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2024-27891 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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