CVE-2026-21916
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA symlink following vulnerability in Junos OS CLI allows authenticated low-privilege users to escalate to root by performing a 'file link ...' operation followed by another user committing configuration changes, enabling full system compromise.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 23.2= 23.2= 23.4= 24.2= 24.4= 25.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine Junos OS versionExecute 'show version' or 'show version detail' in the CLI to obtain the installed Junos OS versionAffected if The installed version matches < 23.2, = 23.2, = 23.4, = 24.2, = 24.4, or = 25.2 (compare your exact version string to the listed affected versions)
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Verify user privilege level for file operationsCheck if the authenticated low-privilege user has access to the 'file link' CLI operation by attempting to run 'file link ?' or reviewing the user's login class and system permission grantsAffected if The user can access the 'file link' command operation (the vulnerability requires this operation to be available to low-privilege users)
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Confirm multi-user configuration environmentDetermine if multiple users have the ability to commit configuration changes in the Junos environmentAffected if Multiple users can perform configuration commits (the attack requires another user to commit configuration changes after the 'file link' operation)
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Check for recent file link operationsReview system logs and audit records for recent 'file link' CLI operations performed by non-privileged usersAffected if Any 'file link' operations have been executed recently by low-privilege accounts in the environment
You are affected if your Junos OS version is exactly 23.2, 23.4, 24.2, 24.4, or 25.2 (or any version below 23.2), AND low-privilege users have access to the 'file link' CLI command in an environment where other users can commit configuration changes.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped23.2
Upgrade Junos OS to version 25.4R1 or later, or to the specified patched versions (23.2R2-S7, 23.4R2-S6, 24.2R2-S3, 24.4R2-S2, or 25.2R2) for each respective branch.
Upgrade to 23.2R2-S7+ / 23.4R2-S6+ / 24.2R2-S3+ / 24.4R2-S2+ / 25.2R2+ depending on current branch
- Identify the current Junos OS version using 'show version' command
- Determine which upgrade path applies based on current version branch (23.2, 23.4, 24.2, 24.4, or 25.2)
- Schedule a maintenance window for the upgrade
- Backup the current configuration using 'request system backup' or 'save' command
- Upgrade to a fixed release: 23.2R2-S7 or later, 23.4R2-S6 or later, 24.2R2-S3 or later, 24.4R2-S2 or later, or 25.2R2 or later
- After upgrade, verify the version using 'show version'
- Confirm the vulnerability is resolved by ensuring the 'file link' command behavior is secure
- Restart any affected services if prompted
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-21916 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-21916 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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