EOS: Insufficient Verification of Data Authenticity
CVE-2026-73437 is a critical-severity insufficient verification of data authenticity vulnerability in EOS from Arista Networks, with a CVSS 3.1 base score of 9.6 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. Affected EOS versions: 4.36.0 through 4.36.1F; 4.35.0 through 4.35.5M; 4.34.0 through 4.34.7.1M, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.21% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of EOS you run against the affected versions below, and install the vendor's latest release.
- 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 | 4.36.0 through 4.36.1F; 4.35.0 through 4.35.5M; 4.34.0 through 4.34.7.1M; 4.33.0 through 4.33.9M | Not stated |
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
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (arista.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.5 | Medium | CNA (arista.com) |
| CVSS 3.1 | 9.6 | Critical | CNA (arista.com) |
Official description
On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay configured, an unauthenticated attacker with network access could send a crafted DHCP reply packet from an IP address that is not configured as a helper address, and the relay agent would forward it to clients without validating the source. This could allow the attacker to supply clients with malicious network configuration parameters, potentially resulting in traffic interception or denial of service for affected clients.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Insufficient Verification of Data Authenticity
The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
More Insufficient Verification of Data Authenticity vulnerabilities (CWE-345)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- 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 Insufficient Verification of Data Authenticity vulnerabilities
- 8.2 High severity
- 8.6 High severity
- 8.3 High severity
- 9.8 Critical severity
- 7.5 High severity
- 9.1 Critical severity
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