# CVE-2020-1637: Junos OS: SRX Series: Unified Access Control (UAC) bypass vulnerability

> Attackers can bypass Unified Access Control policies on Juniper SRX devices to access restricted network resources when specific IP range configurations are used.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Apr 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-v5h6-rmj4-6h5m

## What is CVE-2020-1637?

CVE-2020-1637 is a high-severity authentication bypass vulnerability in Juniper Junos, published on 8 Apr 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in Juniper Networks SRX Series device configured as a Junos OS Enforcer device may allow a user to access network resources that are not permitted by a UAC policy. This issue might occur when the IP address range configured in the Infranet Controller (IC) is configured as an IP address range instead of an IP address/netmask. See the Workaround section for more detail. The Junos OS Enforcer CLI settings are disabled by default. This issue affects Juniper Networks Junos OS on SRX Series: 12.3X48 versions prior to 12.3X48-D100; 15.1X49 versions prior to 15.1X49-D210; 17.3 versions prior to 17.3R2-S5, 17.3R3-S8; 17.4 versions prior to 17.4R2-S9, 17.4R3-S1; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3; 18.3 versions prior to 18.3R1-S7, 18.3R3-S2; 18.4 versions prior to 18.4R1-S6, 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R1-S4, 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S3, 19.2R2; 19.3 versions prior to 19.3R2-S1, 19.3R3; 19.4 versions prior to 19.4R1-S1, 19.4R2.

Weakness: CWE-287 (Improper Authentication), CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2020-1637?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1637?

No fix has been published for CVE-2020-1637 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1637 being exploited?

There is no known exploitation of CVE-2020-1637 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-2020-1637 and fix it if it is affected.

What it is: CVE-2020-1637 is a high-severity authentication bypass vulnerability in Juniper Junos, published on 8 Apr 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-2020-1637 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-2020-1637/ (Markdown: https://insights.sbomify.com/CVE-2020-1637/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1637
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1637
- OSV: https://osv.dev/vulnerability/CVE-2020-1637

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1637/
Summaries are generated and may contain mistakes; the official description above is the record.