# CVE-2025-52947: Junos OS: ACX Series: When 'hot-standby' mode is configured for an L2 circuit, interface flap causes the FEB to crash

> Attackers can crash the Forwarding Engine Board on Juniper ACX routers by flapping interfaces when hot-standby mode is enabled.

- **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/R:A/RE:M/U:Green`)
- **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:** 11 Jul 2025
- **Updated:** 11 Jul 2025
- **Also known as:** GHSA-xw3x-vr3j-962f

## What is CVE-2025-52947?

CVE-2025-52947 is a high-severity denial of service vulnerability in Juniper Junos, published on 11 Jul 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An Improper Handling of Exceptional Conditions vulnerability in route processing of Juniper Networks Junos OS on specific end-of-life (EOL) ACX Series platforms allows an attacker to crash the Forwarding Engine Board (FEB) by flapping an interface, leading to a Denial of Service (DoS).

On ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096 devices, FEB0 will crash when the primary path port of the L2 circuit IGP (Interior Gateway Protocol) on the local device goes down. This issue is seen only when 'hot-standby' mode is configured for the L2 circuit.

This issue affects Junos OS on ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096: 

  *  all versions before 21.2R3-S9.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2025-52947?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2025-52947?

No fix has been published for CVE-2025-52947 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-52947 being exploited?

There is no known exploitation of CVE-2025-52947 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-2025-52947 and fix it if it is affected.

What it is: CVE-2025-52947 is a high-severity denial of service vulnerability in Juniper Junos, published on 11 Jul 2025. 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-2025-52947 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-2025-52947/ (Markdown: https://insights.sbomify.com/CVE-2025-52947/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-52947
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-52947
- OSV: https://osv.dev/vulnerability/CVE-2025-52947

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-52947/
Summaries are generated and may contain mistakes; the official description above is the record.