# CVE-2026-121370: Arista EOS denial of service in PTP

Source: https://junglewise.ai/threats/cve-2026-121370-on-affected-platforms-running-arista-eos-with-precision-time  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-121370 · Severity: high · CVSS 8.6 · Published 2026-11-10

Arista EOS is a network operating system used on switches and routing platforms. An attacker with network access to a Precision Time Protocol (PTP) port can send crafted traffic that exhausts the system's processing resources, causing a denial of service and preventing legitimate network traffic from being handled. This affects only 750X series switches with PTP enabled.

Technologies: [Arista Eos](https://junglewise.ai/threats/technologies/eos). Vendors: [Arista](https://junglewise.ai/threats/vendors/arista).

## Quick answers

**Is CVE-2026-121370 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121370 being exploited in the wild.

**How severe is CVE-2026-121370?** High severity, with a CVSS score of 8.6, published 10 November 2026.

**Which products and versions are affected?** Arista Eos 4.34.1F and below (4.34.x), 4.33.8M and below (4.33.x), all 4.32.x, all 4.31.x, all 4.30.x, 4.29.2F and later (4.29.x End of Support).

**Is there a fix for CVE-2026-121370?** No fixed version is recorded yet. A bandwidth limit can be applied to the PTP CPU queue by disabling PTP on affected interfaces, then running platform commands to set MMU_MAX_BUCKET_QLAYER and MMU_MIN_BUCKET_QLAYER thresholds. These settings are not persistent across forwarding plane resets or line card replacements.</anigation>
<parameter name="timeline">[{"kind":"disclosed","at":"2026-11-10"}] If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-121370 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-121370?** Check whether you run Arista Eos at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix


A bandwidth limit can be applied to the PTP CPU queue by disabling PTP on affected interfaces, then running platform commands to set MMU_MAX_BUCKET_QLAYER and MMU_MIN_BUCKET_QLAYER thresholds. These settings are not persistent across forwarding plane resets or line card replacements.</anigation>
<parameter name="timeline">[{"kind":"disclosed","at":"2026-11-10"}]

## Technical details

An unauthenticated attacker with network access to a PTP-enabled interface can trigger a resource exhaustion vulnerability (CWE-770) by sending traffic to the PTP CPU queue, causing high CPU utilization and preventing control-plane traffic processing. Exploitation requires PTP to be configured and at least one interface enabled globally. A bandwidth limit mitigation can be applied via CLI commands to throttle the PTP CPU queue.

## Affected products

- Arista EOS 4.34.1F and below (4.34.x), 4.33.8M and below (4.33.x), all 4.32.x, all 4.31.x, all 4.30.x, 4.29.2F and later (4.29.x End of Support)

## References

- [https://www.arista.com/en/support/advisories-notices/security-advisory/25046-security-advisory-0224](https://www.arista.com/en/support/advisories-notices/security-advisory/25046-security-advisory-0224)

## Related threats

- [Arista EOS path traversal in eAPI service](https://junglewise.ai/threats/cve-2026-121371-on-affected-eos-versions-with-the-eapi-service-enabled-a)
- [Arista EOS denial of service via resource exhaustion](https://junglewise.ai/threats/cve-2026-121369-on-affected-platforms-running-arista-eos-under-specific-link)
- [Arista EOS BFD authentication out-of-bounds write](https://junglewise.ai/threats/cve-2026-121368-on-affected-platforms-running-arista-eos-with-bidirectional)
- [Arista EOS RIPv2 silent enablement on management interfaces](https://junglewise.ai/threats/cve-2026-121367-on-affected-arista-eos-platforms-with-routing-information)
- [Arista EOS kernel crash via crafted S-BFD PDU](https://junglewise.ai/threats/cve-2026-121295-on-affected-platforms-running-arista-eos-configured-as-s-bfd)