CVE-2026-21916 | Junos OS: A low privileged user can escalate their privileges so that they can login as root

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: 2026-04-09 Last update: 2026-04-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-21916 is rated Low Risk (28.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.01%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-21916

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-10 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-21916

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.0 4.0 HIGH
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:X/RE:M/U:X Click to expand
Attack vector (AV:L)
Attacker needs local access on the target system.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:L)
Low privileges are required.
User interaction (UI:P)
A user has to participate (for example click/open/approve).
Vulnerable system confidentiality impact (VC:H)
High confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:H)
High integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H)
High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:L)
Limited availability impact on subsequent systems.
Exploit maturity (threat) (E:X)
Not defined: no reliable threat intelligence; scoring assumes the worst case (equivalent to Attacked).
Confidentiality requirement (CR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Integrity requirement (IR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Availability requirement (AR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Modified attack vector (MAV:X)
Not defined: scoring uses the Base Attack Vector (AV).
Modified attack complexity (MAC:X)
Not defined: scoring uses the Base Attack Complexity (AC).
Modified attack requirements (MAT:X)
Not defined: scoring uses the Base Attack Requirements (AT).
Modified privileges required (MPR:X)
Not defined: scoring uses the Base Privileges Required (PR).
Modified user interaction (MUI:X)
Not defined: scoring uses the Base User Interaction (UI).
Modified vulnerable system confidentiality impact (MVC:X)
Not defined: scoring uses the Base VC metric.
Modified vulnerable system integrity impact (MVI:X)
Not defined: scoring uses the Base VI metric.
Modified vulnerable system availability impact (MVA:X)
Not defined: scoring uses the Base VA metric.
Modified subsequent system confidentiality impact (MSC:X)
Not defined: scoring uses the Base SC metric.
Modified subsequent system integrity impact (MSI:X)
Not defined: scoring uses the Base SI metric.
Modified subsequent system availability impact (MSA:X)
Not defined: scoring uses the Base SA metric.
Safety (supplemental) (S:X)
Not evaluated.
Automatable (supplemental) (AU:Y)
Yes: all four kill-chain steps (reconnaissance, weaponization, delivery, exploitation) can be automated.
Recovery (supplemental) (R:U)
User: manual user intervention is needed to recover services.
Value density (supplemental) (V:X)
Not evaluated.
Vulnerability response effort (supplemental) (RE:M)
Moderate effort (remote update, disable subsystem, simple upgrade with minor service impact).
Provider urgency (supplemental) (U:X)
Not evaluated.
 — — [email protected]
7.3 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.3 5.9 [email protected]

Weakness enumeration for CVE-2026-21916

Affected software / configurations for CVE-2026-21916

Vendor Product Version Raw CPE
juniper junos < 23.2 cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:-:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s1:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s2:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s3:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s4:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s5:*:*:*:*:*:*
juniper junos 23.2 cpe:2.3:o:juniper:junos:23.2:r2-s6:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r1-s2:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2-s1:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2-s2:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2-s3:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2-s4:*:*:*:*:*:*
juniper junos 23.4 cpe:2.3:o:juniper:junos:23.4:r2-s5:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:-:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r1:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r1-s1:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r1-s2:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r2:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r2-s1:*:*:*:*:*:*
juniper junos 24.2 cpe:2.3:o:juniper:junos:24.2:r2-s2:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:-:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:r1:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:r1-s2:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:r1-s3:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:r2:*:*:*:*:*:*
juniper junos 24.4 cpe:2.3:o:juniper:junos:24.4:r2-s1:*:*:*:*:*:*
juniper junos 25.2 cpe:2.3:o:juniper:junos:25.2:-:*:*:*:*:*:*
juniper junos 25.2 cpe:2.3:o:juniper:junos:25.2:r1:*:*:*:*:*:*
juniper junos 25.2 cpe:2.3:o:juniper:junos:25.2:r1-s1:*:*:*:*:*:*
juniper junos 25.2 cpe:2.3:o:juniper:junos:25.2:r1-s2:*:*:*:*:*:*

References for CVE-2026-21916

URL Tags
https://kb.juniper.net/JSA107807 Mitigation Vendor Advisory
cvelogic Threat Intelligence