# CVE-2019-0053: Junos OS: Insufficient validation of environment variables in telnet client may lead to stack-based buffer overflow

> Stack-based buffer overflow in Junos OS telnet client allows bypassing veriexec restrictions, potentially leading to privilege escalation or code execution.

- **Severity:** High 7.8 (`CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Jul 2019
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2019-0053, GHSA-4vvc-hp8x-p32m, UBUNTU-CVE-2019-0053

## What is CVE-2019-0053?

CVE-2019-0053 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 11 Jul 2019. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Insufficient validation of environment variables in the telnet client supplied in Junos OS can lead to stack-based buffer overflows, which can be exploited to bypass veriexec restrictions on Junos OS. A stack-based overflow is present in the handling of environment variables when connecting via the telnet client to remote telnet servers. This issue only affects the telnet client — accessible from the CLI or shell — in Junos OS. Inbound telnet services are not affected by this issue. This issue affects: Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S13; 12.3X48 versions prior to 12.3X48-D80; 14.1X53 versions prior to 14.1X53-D130, 14.1X53-D49; 15.1 versions prior to 15.1F6-S12, 15.1R7-S4; 15.1X49 versions prior to 15.1X49-D170; 15.1X53 versions prior to 15.1X53-D237, 15.1X53-D496, 15.1X53-D591, 15.1X53-D69; 16.1 versions prior to 16.1R3-S11, 16.1R7-S4; 16.2 versions prior to 16.2R2-S9; 17.1 versions prior to 17.1R3; 17.2 versions prior to 17.2R1-S8, 17.2R2-S7, 17.2R3-S1; 17.3 versions prior to 17.3R3-S4; 17.4 versions prior to 17.4R1-S6, 17.4R2-S3, 17.4R3; 18.1 versions prior to 18.1R2-S4, 18.1R3-S3; 18.2 versions prior to 18.2R1-S5, 18.2R2-S2, 18.2R3; 18.2X75 versions prior to 18.2X75-D40; 18.3 versions prior to 18.3R1-S3, 18.3R2; 18.4 versions prior to 18.4R1-S2, 18.4R2.

Weakness: CWE-787 (Out-of-bounds Write), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2019-0053?

It affects 2 products.


Products: Debian Debian Linux, Juniper Junos.

## How do I fix CVE-2019-0053?

Upgrade to a fixed version.

## Is CVE-2019-0053 being exploited?

There is no known exploitation of CVE-2019-0053 in the wild and no public exploit code.

Public exploit code:

- A patched Arch Linux PKGBUILD to address CVE-2019-0053 (buffer overflow). Downloads and applies a (currently) unreleased patch from upstream. (github_poc): https://github.com/dreamsmasher/inetutils-CVE-2019-0053-Patched-PKGBUILD

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-0053 and fix it if it is affected.

What it is: CVE-2019-0053 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 11 Jul 2019. 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-2019-0053 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2019-0053/ (Markdown: https://insights.sbomify.com/CVE-2019-0053/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-0053
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-0053
- OSV: https://osv.dev/vulnerability/CVE-2019-0053

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-0053/
Summaries are generated and may contain mistakes; the official description above is the record.