# CVE-2026-120978: Arista EOS denial of service in BGP-LS

Source: https://junglewise.ai/threats/cve-2026-120978-on-affected-arista-eos-platforms-running-border-gateway-protocol  
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-2026-120978 · Severity: medium · CVSS 6.5 · Published 2026-11-10

Arista EOS network operating system running Border Gateway Protocol with Link State (BGP-LS) in Dynamic Path Selection consumer mode contains a flaw that allows an authenticated attacker to crash the BGP routing service with a crafted message. This causes the routing process to restart unexpectedly, disrupting network traffic and potentially creating an outage in production networks.

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

## Quick answers

**Is CVE-2026-120978 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120978 being exploited in the wild.

**How severe is CVE-2026-120978?** Medium severity, with a CVSS score of 6.5, published 10 November 2026.

**Which products and versions are affected?** Arista Eos 4.36.2F and below in 4.36.x; 4.35.6M and below in 4.35.x; 4.34.8M and below in 4.34.x; 4.33.10M and below in 4.33.x; all 4.32.x releases; all End of Support releases.

**Is there a fix for CVE-2026-120978?** Yes: fixed in 4.37.0F and later (4.37.x); 4.36.3M and later (4.36.x); 4.35.7M and later (4.35.x); 4.34.9M and later (4.34.x); 4.33.11M and later (4.33.x). Until then: No configuration-level mitigations are available; software upgrade is required to fully resolve the issue. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-120978 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-120978?** 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

- Fixed in 4.37.0F and later (4.37.x); 4.36.3M and later (4.36.x); 4.35.7M and later (4.35.x); 4.34.9M and later (4.34.x); 4.33.11M and later (4.33.x)

No configuration-level mitigations are available; software upgrade is required to fully resolve the issue.

## Technical details

A null pointer dereference or reachable assertion in the BGP-LS message handling code allows an authenticated BGP peer to trigger a BGP agent restart. The vulnerability requires an established BGP-LS peer session with the device configured as a Dynamic Path Selection consumer; an attacker must have network access and valid BGP credentials to exploit it. The attack results in denial of service to the BGP service on the affected platform.

## Affected products

- Arista EOS 4.36.2F and below in 4.36.x; 4.35.6M and below in 4.35.x; 4.34.8M and below in 4.34.x; 4.33.10M and below in 4.33.x; all 4.32.x releases; all End of Support releases

## Timeline

- 2026-11-10: disclosed

## References

- [https://www.arista.com/en/support/advisories-notices/security-advisory/25033-security-advisory-0211](https://www.arista.com/en/support/advisories-notices/security-advisory/25033-security-advisory-0211)

## 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)