CVE-2026-121368Arista Networks EOS out-of-bounds write
CVE-2026-121368 is a out-of-bounds write in Arista Networks EOS, rated high (8.9 on CVSS 4.0).
Why this priority: High severity, with no exploitation signal yet.
Published · Updated · NVD status: Received
What it is
Code writes past the end of a buffer, corrupting memory in ways an attacker can often turn into code execution.
How it is reached
An attacker can exploit it over the network, without an account, and nobody has to click anything. Success also depends on conditions the attacker does not fully control.
What an attacker gains
A successful attack can take it offline. In practice, this kind of flaw lets an attacker crash the process, read memory, or in the worst case run code. The damage can spread past the vulnerable component into others.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade Arista Networks EOS to a fixed version for your release line (4.33.0F, 4.32.0F).
- Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
Description from NVD
On affected platforms running Arista EOS with Bidirectional Forwarding Detection (BFD) configured to use keyed MD5 or keyed SHA1 authentication, an unauthenticated attacker with network adjacency (direct or multi-hop) to a BFD-enabled interface can send a specially crafted BFD packet resulting in a system reboot.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Native code: operating systems, browsers and firmware. The flaw sits wherever native code reads untrusted data.
- Network appliances and media or file parsers. The flaw sits wherever native code reads untrusted data.
Trust boundaries in play
- Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
- Isolation between components. The impact crosses out of the vulnerable component into others it should be isolated from.
- Wherever native code reads untrusted data. An attacker who crosses it can crash the process, read memory, or in the worst case run code.
Questions to answer about your own systems
- Where does Arista Networks EOS run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.