# 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.

- **Severity:** Medium 6.0 (`CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-738x-gmrv-v9j5

## 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 (Improper Input Validation)

## 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.

## Is CVE-2026-77190 being exploited?

There is no known exploitation of CVE-2026-77190 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77190 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-77190 in the wild and no public exploit code.

Affected product: Arista Networks EOS. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77190/ (Markdown: https://insights.sbomify.com/CVE-2026-77190/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77190
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77190
- OSV: https://osv.dev/vulnerability/CVE-2026-77190

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77190/
Summaries are generated and may contain mistakes; the official description above is the record.