EOS: Improper Access Control
CVE-2026-120983 is a high-severity improper access control vulnerability in EOS from Arista Networks, with a CVSS 3.1 base score of 7.6 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists version 4.33.0F as the first without the flaw, so updating EOS to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update EOS to 4.33.0F or a later version.
- Read the advisory on arista.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Arista Networks | EOS | 1.0.0 up to, but not including, 4.33.0F; 4.33.0F through 4.33.9M; 4.34.0F through 4.34.7M; 4.35.0F through 4.35.5M; 4.36.0F through 4.36.1F | 4.33.0F |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L. Scored by CNA (arista.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.1 | Medium | CNA (arista.com) |
| CVSS 3.1 | 7.6 | High | CNA (arista.com) |
Official description
On affected EOS platforms where 802.1x is configured in multi-host authenticated mode and the device is configured with Policy Based Routing (PBR), traffic from unauthenticated hosts may be forwarded to the destination configured in the PBR policies. This could potentially allow unauthenticated hosts access to networks. Additionally Layer 2 and Layer 3 control packets from unauthenticated hosts may get copied to the CPU.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Access Control
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
How developers prevent this class of flaw
- Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in EOS
- 7.5 High severity
- 8.6 High severity
- 8.6 High severity
- 9.6 Critical severity
- 8.6 High severity
- 8.2 High severity
Recent Improper Access Control vulnerabilities
- 7.3 High severity
- 7.5 High severity
- 7.3 High severity
- 7.1 High severity
- 7.5 High severity
- 9.1 Critical severity
Spotted an error? Tell us.