EOS: Expected Behavior Violation
CVE-2026-120982 is a high-severity expected behavior violation vulnerability in EOS from Arista Networks, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the 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 0.35% 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.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Arista Networks | EOS | 4.36.0F through 4.36.2F; 4.35.0F through 4.35.6M; 4.34.0F through 4.34.8M; 4.33.0F through 4.33.10M; 1.0.0 up to, but not including, 4.33.0F | 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
- NetworkCan be exploited remotely over a network, including the internet.
- 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
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (arista.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.7 | High | CNA (arista.com) |
| CVSS 3.1 | 7.5 | High | CNA (arista.com) |
Official description
On affected platforms running Arista EOS with Border Gateway Protocol (BGP) configured, An unauthenticated attacker who can establish a BGP peering session with an affected device and can send specially crafted BGP messages to cause repeated BGP session resets, enabling sustained disruption to network routing and traffic forwarding.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Expected Behavior Violation
A feature, API, or function does not perform according to its specification.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, 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 Expected Behavior Violation vulnerabilities
- 7.1 High severity
- 8.7 High severity
- 8.8 High severity
- 9.0 Critical severity
- 7.1 High severity
- 7.8 High severity
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