# CVE-2026-121295: Arista EOS kernel crash via crafted S-BFD PDU

Source: https://junglewise.ai/threats/cve-2026-121295-on-affected-platforms-running-arista-eos-configured-as-s-bfd  
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-2026-121295 · Severity: high · CVSS 8.6 · Published 2026-11-10

Arista EOS is a network operating system used on switches and routers. An attacker on the network can send a specially crafted S-BFD (Seamless Bidirectional Forwarding Detection) packet to a device configured as an S-BFD initiator, causing the device's kernel to crash and reboot unexpectedly. This results in network outage and disruption of services on affected network switches.

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

## Quick answers

**Is CVE-2026-121295 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121295 being exploited in the wild.

**How severe is CVE-2026-121295?** High severity, with a CVSS score of 8.6, published 10 November 2026.

**Which products and versions are affected?** Arista Eos 4.36.2F and below (4.36.x train), 4.35.6M and below (4.35.x train), 4.34.8M and below (4.34.x train), 4.33.10M and below (4.33.x train), all 4.32.x, all 4.31.x, 4.30.x, 4.29.x, 4.28.2F and later of 4.28.x (end-of-support releases).

**Is there a fix for CVE-2026-121295?** No fixed version is recorded yet. Check the vendor's advisory in the references below. 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-2026-121295 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-121295?** 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.

## Technical details

The vulnerability exists in Arista EOS's handling of S-BFD PDUs on devices configured as S-BFD initiators with round-trip delay measurement enabled. An unauthenticated network attacker can send a crafted S-BFD PDU that triggers improper input validation (CWE-1284), causing a kernel crash and device reboot. No authentication, user interaction, or local access is required; the attack is purely network-based.

## Affected products

- Arista EOS 4.36.2F and below (4.36.x train), 4.35.6M and below (4.35.x train), 4.34.8M and below (4.34.x train), 4.33.10M and below (4.33.x train), all 4.32.x, all 4.31.x, 4.30.x, 4.29.x, 4.28.2F and later of 4.28.x (end-of-support releases)

## Timeline

- 2026-11-10: advisory

## References

- [https://www.arista.com/en/support/advisories-notices/security-advisory/25045-security-advisory-0223](https://www.arista.com/en/support/advisories-notices/security-advisory/25045-security-advisory-0223)

## 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 in PTP](https://junglewise.ai/threats/cve-2026-121370-on-affected-platforms-running-arista-eos-with-precision-time)
- [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)