# CVE-2020-1662: Junos OS and Junos OS Evolved: RPD crash due to BGP session flapping.

> A remote attacker can cause a routing process daemon crash and restart on Juniper devices by triggering BGP session flapping under specific configuration conditions.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-8vq7-pm9r-4fgw

## What is CVE-2020-1662?

CVE-2020-1662 is a high-severity denial of service vulnerability in Juniper Junos, published on 16 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On Juniper Networks Junos OS and Junos OS Evolved devices, BGP session flapping can lead to a routing process daemon (RPD) crash and restart, limiting the attack surface to configured BGP peers. This issue only affects devices with BGP damping in combination with accepted-prefix-limit configuration. When the issue occurs the following messages will appear in the /var/log/messages: rpd[6046]: %DAEMON-4-BGP_PREFIX_THRESH_EXCEEDED: XXXX (External AS x): Configured maximum accepted prefix-limit threshold(1800) exceeded for inet6-unicast nlri: 1984 (instance master) rpd[6046]: %DAEMON-3-BGP_CEASE_PREFIX_LIMIT_EXCEEDED: 2001:x:x:x::2 (External AS x): Shutting down peer due to exceeding configured maximum accepted prefix-limit(2000) for inet6-unicast nlri: 2001 (instance master) rpd[6046]: %DAEMON-4: bgp_rt_maxprefixes_check_common:9284: NOTIFICATION sent to 2001:x:x:x::2 (External AS x): code 6 (Cease) subcode 1 (Maximum Number of Prefixes Reached) AFI: 2 SAFI: 1 prefix limit 2000 kernel: %KERN-5: mastership_relinquish_on_process_exit: RPD crashed on master RE. Sending SIGUSR2 to chassisd (5612:chassisd) to trigger RE switchover This issue affects: Juniper Networks Junos OS: 17.2R3-S3; 17.3 version 17.3R3-S3 and later versions, prior to 17.3R3-S8; 17.4 version 17.4R2-S4, 17.4R3 and later versions, prior to 17.4R2-S10, 17.4R3-S2; 18.1 version 18.1R3-S6 and later versions, prior to 18.1R3-S10; 18.2 version 18.2R3 and later versions, prior to 18.2R3-S4; 18.2X75 version 18.2X75-D50, 18.2X75-D60 and later versions, prior to 18.2X75-D53, 18.2X75-D65; 18.3 version 18.3R2 and later versions, prior to 18.3R2-S4, 18.3R3-S2; 18.4 version 18.4R2 and later versions, prior to 18.4R2-S5, 18.4R3-S2; 19.1 version 19.1R1 and later versions, prior to 19.1R2-S2, 19.1R3-S1; 19.2 version 19.2R1 and later versions, prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2; 20.1 versions prior to 20.1R1-S2, 20.1R2. Juniper Networks Junos OS Evolved prior to 20.1R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R3-S3.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2020-1662?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1662?

No fix has been published for CVE-2020-1662 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1662 being exploited?

There is no known exploitation of CVE-2020-1662 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-2020-1662 and fix it if it is affected.

What it is: CVE-2020-1662 is a high-severity denial of service vulnerability in Juniper Junos, published on 16 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-1662 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-2020-1662/ (Markdown: https://insights.sbomify.com/CVE-2020-1662/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1662
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1662
- OSV: https://osv.dev/vulnerability/CVE-2020-1662

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1662/
Summaries are generated and may contain mistakes; the official description above is the record.