# CVE-2026-57020: Junos OS: QFX10000 Series: IPv6 multicast traffic received on non-IRB interfaces causes a multicast flood

> An unauthenticated adjacent attacker can cause a denial of service by sending IPv6 multicast traffic to non-IRB interfaces on QFX10000 switches in EVPN-VxLAN scenarios.

- **Severity:** High 7.1 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M`)
- **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:** 9 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** GHSA-vhf9-x75x-qgv5

## What is CVE-2026-57020?

CVE-2026-57020 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on QFX10000 Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).

On all QFX10000 platforms in an EVPN-VxLAN scenario, if an attacker sends IPv6 multicast traffic and these packets reach the non-IRB interface of a spine switch it floods the packet to other spines and all Ethernet Segment Identifier (ESI) leaf switches. This flooding causes the packet to be forwarded in a endless loop, which can lead to saturation of the involved links and in turn impact to legitimate traffic.

This issue affects Junos OS on QFX10000 Series:

  *  all versions before 23.2R2-S7,
  *  23.4 versions before 23.4R2-S8,
  *  24.2 versions before 24.2R2-S4,
  *  24.4 versions before 24.4R2-S4.

This issue does not affect Junos version after 24.4 as the QFX10000 Series devices are not supported on newer versions anymore.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2026-57020?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2026-57020?

No fix has been published for CVE-2026-57020 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57020 being exploited?

There is no known exploitation of CVE-2026-57020 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos

- [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild)
- [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild)
- [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild)
- [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild)
- [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57020 and fix it if it is affected.

What it is: CVE-2026-57020 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Jul 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-2026-57020 in the wild and no public exploit code.

Affected product: Juniper Junos. 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-2026-57020/ (Markdown: https://insights.sbomify.com/CVE-2026-57020/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57020
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57020
- OSV: https://osv.dev/vulnerability/CVE-2026-57020

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57020/
Summaries are generated and may contain mistakes; the official description above is the record.