Quick answers
- Is CVE-2026-121286 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-121286 being exploited in the wild.
- How severe is CVE-2026-121286?
- 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 (4.36.x); 4.35.6M and below (4.35.x); 4.34.8M and below (4.34.x); 4.33.10M and below (4.33.x); all 4.32.x; 4.22.1F–4.31.x.
- Is there a fix for CVE-2026-121286?
- Yes: fixed in EOS 4.37.0F and later, 4.36.3M and later, 4.35.7M and later, 4.34.9M and later, 4.33.11M and later. Until then: Contact Arista Technical Assistance Center (TAC) for mitigation guidance. The vulnerability requires multi-agent routing model with BGP SR-TE address families configured; disabling SR-TE or reverting to single-agent routing mode would prevent exploitation.</anigation> <parameter name="timeline">[{"kind": "advisory", "at": "2026-11-10"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-121286 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-121286?
- 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: EOS 4.37.0F and later, 4.36.3M and later, 4.35.7M and later, 4.34.9M and later, 4.33.11M and later
Contact Arista Technical Assistance Center (TAC) for mitigation guidance. The vulnerability requires multi-agent routing model with BGP SR-TE address families configured; disabling SR-TE or reverting to single-agent routing mode would prevent exploitation.</anigation> <parameter name="timeline">[{"kind": "advisory", "at": "2026-11-10"}]
Technical details
A null pointer dereference in the BGP process occurs when processing crafted BGP packets in a multi-agent routing model with Segment Routing Traffic Engineering (SR-TE) address families configured and an established BGP neighbor. An authenticated BGP peer on the network can trigger this by sending malformed packets, causing repeated BGP process restarts and denial of service to all BGP sessions on the device.
Affected products
- Arista EOS 4.36.2F and below (4.36.x); 4.35.6M and below (4.35.x); 4.34.8M and below (4.34.x); 4.33.10M and below (4.33.x); all 4.32.x; 4.22.1F–4.31.x