EOS: Incorrect Implementation of Authentication Algorithm
CVE-2026-73458 is a high-severity incorrect implementation of authentication algorithm vulnerability in EOS from Arista Networks, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the 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 4.34.7M, 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 0.4% 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
- 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.
- 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 | 4.36.0 through 4.36.1F; 4.35.0 through 4.35.5M; 4.34.0 through 4.34.7M; 4.33.0 through 4.33.8M | 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
- 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
- LowLimited modification of data is possible.
- 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:L/A:H. Scored by CNA (arista.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.2 | Critical | CNA (arista.com) |
| CVSS 3.1 | 8.2 | High | CNA (arista.com) |
Official description
On affected platforms running Arista EOS with authenticated Bidirectional Forwarding Detection (BFD) sessions configured, a specially crafted packet can cause the BFD session(s) to go down. This may result in undesirable network changes because various routing protocols monitor status on BFD session(s).
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Implementation of Authentication Algorithm
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.
More Incorrect Implementation of Authentication Algorithm vulnerabilities (CWE-303)
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 Incorrect Implementation of Authentication Algorithm vulnerabilities
- 9.2 Critical severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.3 High severity
- 9.8 Critical severity
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