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NVD / CVE Program· CNA Arista

CVE-2021-28511: 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 sec

Noroxi assessment

Priority: Monitor (action score 26/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.59% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.5 · v3.1—No exploit No fix recorded
Published
Aug 5, 2022
Updated
Jun 16, 2026
EPSS
0.5% · 48th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · Arista
5.8
0.7 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-28511

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
aristaeos
arista7050cx3-32s
arista7050cx3m-32s
arista7050sx3-48c8
arista7050sx3-48yc
arista7050sx3-48yc12
arista7050sx3-48yc8
arista7050sx3-96yc8
arista7050tx3-48c8
arista720xp-24y6
arista720xp-24zy4
arista720xp-48y6

and 4 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • arista eosup to 4.24.9 inclusive
  • arista eos4.25.0 and later · up to 4.25.8 inclusive
  • arista eos4.26.0 and later · up to 4.26.5 inclusive
  • arista eos4.27.0 and later · up to 4.27.3 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Arista). Independent of NVD's CPE analysis and usually ahead of it.

  • Arista Networks EOS

    • 4.24.0 and later · up to and including 4.24.9affected
    • 4.25.0 and later · up to and including 4.25.8affected
    • 4.26.0 and later · up to and including 4.26.5affected
    • 4.27.0 and later · up to and including 4.27.3affected

Same product

arista: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-7473Arista EOS Unexpected Tunnel Protocol Decapsulation and Forwarding BypassKEV
    60This week
  • CVE-2015-8236Arista EOS before 4.11.12, 4.12 before 4.12.11, 4.13 before 4.13.14M, 4.14 before 4.14.5FX.5, and 4.15 before 4.15.0FX1.1 allows remote atta
    41Plan
  • CVE-2021-28503In Arista's EOS software affected releases, eAPI might skip re-evaluating user credentials when certificate based authentication is used, which allows remote at
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-28504Apr 1, 2022 · On Arista Strata family products which have “TCAM profile” feature enabled when Port IPv4 access-list has a rule which matches on “vxlan” as protocol then that
    30Monitor
  • ← EarlierCVE-2021-28505Apr 14, 2022 · On affected Arista EOS platforms, if a VXLAN match rule exists in an IPv4 access-list that is applied to the ingress of an L2 or an L3 port/SVI, the VXLAN rule
    30Monitor
  • Later →CVE-2021-28510Jan 26, 2023 · For certain systems running EOS, a Precision Time Protocol (PTP) packet of a management/signaling message with an invalid Type-Length-Value (TLV) causes the PTP
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-284 · Improper Access Control

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

All records