CVE-2026-77190 Security Advisory 0177
An unauthenticated network-adjacent attacker can cause a sustained denial of service on Arista EOS switches by sending malformed PIM messages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77190?
CVE-2026-77190 is a medium-severity denial of service vulnerability in Arista Networks EOS, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
On affected platforms running Arista EOS, an unauthenticated attacker who is network-adjacent to the switch and able to connect to a device with PIM Sparse Mode and MLAG configured, can send malformed messages that cause the Pimsm agent to terminate unexpectedly. The Pimsm agent is automatically restarted, but repeated attacks can cause the agent to restart continuously, resulting in a sustained denial of service.
Weakness: CWE-20
Which versions are affected by CVE-2026-77190?
How do I fix CVE-2026-77190?
No fix has been published for CVE-2026-77190 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-77190 being exploited?
There is no known exploitation of CVE-2026-77190 in the wild and no public exploit code.
Sources
Also known as GHSA-738x-gmrv-v9j5.