Arista EOS: Resource exhaustion via crafted link traffic leading to reboot
Summary
Arista EOS on the 750X Series is affected under specific link configurations. An attacker with direct connectivity to the system can drive CPU and memory utilization up considerably, causing slow responsiveness and possibly a reboot. Authentication and user interaction are not required, but the attacker must be on an adjacent or physical network path. Confidentiality and integrity are not affected.
Affected
- Arista EOS 4.34.2F through 4.34.7M
- Arista EOS 4.35.0F through 4.35.6M
- Arista EOS 4.36.0F through 4.36.1M
- Default configuration: unaffected
- Required configuration: interfaces without an explicit speed setting (speed auto)
Fixed in
Unknown. Check Arista Security Advisory 0225 for the fixed release.
Workaround
- Configure an explicit speed on all interfaces to prevent exposure, for example: speed auto 1g on the affected interface
- Check with 'show active all | grep speed' whether interfaces have no speed configured
- Restrict who can reach the switch's data-plane connections
Exploitation
- Exploited in the wild: no reports found at time of research.
- Public proof of concept: none found.
- CISA KEV: not checked.
Our recommendation
- Check whether any 750X Series units are in your environment and which EOS version they run.
- Read Arista advisory 0225 for the fixed release and configuration guidance, and plan the update.
- Check whether interfaces use the vulnerable link configuration and apply the explicit speed workaround if patching is not immediate.
- Restrict access to the switch's data-plane connections and monitor CPU and memory utilization on affected units.
- Assess related Arista advisory CVE-2026-121370 if you run EOS switches.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Arista Security Advisory 0225 www.arista.com
- CVE Record CVE-2026-121369 www.cve.org
- Vulners ARISTA:0225 vulners.com
- Strix CVE-2026-121369 www.strix.ai
- ThreatInt CVE-2026-121369 cve.threatint.com
- CCS-750 Series Datasheet www.arista.com
- Arista Community: Troubleshooting high CPU utilization arista.my.site.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 11:28.
Original description (NVD)
On affected platforms running Arista EOS under specific link configurations an attacker with direct connectivity to the system may cause system CPU and memory utilization to increase considerably leading to slow responsiveness and eventually may cause the system to reboot.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
Affected? We can help.
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