Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2026-21916 — juniper / junos

UNIX Symbolic Link (Symlink) Following

A UNIX Symbolic Link (Symlink) Following vulnerability in the CLI of Juniper Networks Junos OS allows a local, authenticated attacker with low privileges to escalate their privileges to root which will lead to a complete compromise of the system.

When after a user has performed a specific 'file link ...' CLI operation, another user commits (unrelated configuration changes), the first user can login as root.

This issue affects Junos OS:

  • all versions before 23.2R2-S7,
  • 23.4 versions before 23.4R2-S6,
  • 24.2 versions before 24.2R2-S3,
  • 24.4 versions before 24.4R2-S2,
  • 25.2 versions before 25.2R2.

This issue does not affect versions 25.4R1 or later.

  • Published: Apr 9, 2026
  • Updated: Apr 10, 2026
  • CVE: CVE-2026-21916
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 7.3
  • AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

CWEs:

Software From Fixed in
juniper / junos - 23.2
juniper / junos 23.2 23.2.x
juniper / junos 23.2-r1 23.2-r1.x
juniper / junos 23.2-r1-s1 23.2-r1-s1.x
juniper / junos 23.2-r1-s2 23.2-r1-s2.x
juniper / junos 23.2-r2 23.2-r2.x
juniper / junos 23.2-r2-s1 23.2-r2-s1.x
juniper / junos 23.2-r2-s2 23.2-r2-s2.x
juniper / junos 23.2-r2-s3 23.2-r2-s3.x
juniper / junos 23.2-r2-s4 23.2-r2-s4.x
juniper / junos 23.2-r2-s5 23.2-r2-s5.x
juniper / junos 23.2-r2-s6 23.2-r2-s6.x
juniper / junos 23.4 23.4.x
juniper / junos 23.4-r1 23.4-r1.x
juniper / junos 23.4-r1-s1 23.4-r1-s1.x
juniper / junos 23.4-r1-s2 23.4-r1-s2.x
juniper / junos 23.4-r2 23.4-r2.x
juniper / junos 23.4-r2-s1 23.4-r2-s1.x
juniper / junos 23.4-r2-s2 23.4-r2-s2.x
juniper / junos 23.4-r2-s3 23.4-r2-s3.x
juniper / junos 23.4-r2-s4 23.4-r2-s4.x
juniper / junos 23.4-r2-s5 23.4-r2-s5.x
juniper / junos 24.2 24.2.x
juniper / junos 24.2-r1 24.2-r1.x
juniper / junos 24.2-r1-s1 24.2-r1-s1.x
juniper / junos 24.2-r1-s2 24.2-r1-s2.x
juniper / junos 24.2-r2 24.2-r2.x
juniper / junos 24.2-r2-s1 24.2-r2-s1.x
juniper / junos 24.2-r2-s2 24.2-r2-s2.x
juniper / junos 24.4 24.4.x
juniper / junos 24.4-r1 24.4-r1.x
juniper / junos 24.4-r1-s2 24.4-r1-s2.x
juniper / junos 24.4-r1-s3 24.4-r1-s3.x
juniper / junos 24.4-r2 24.4-r2.x
juniper / junos 24.4-r2-s1 24.4-r2-s1.x
juniper / junos 25.2 25.2.x
juniper / junos 25.2-r1 25.2-r1.x
juniper / junos 25.2-r1-s1 25.2-r1-s1.x
juniper / junos 25.2-r1-s2 25.2-r1-s2.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.