Page generated: 11 Nov 2026, 14:32 UTC
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CVE-2025-21590

An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can comp…

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An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can compromise an affected device. This issue is not exploitable from the Junos CLI. This issue affects Junos OS:  * All versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10,  * 22.2 versions before 22.2R3-S6,  * 22.4 versions before 22.4R3-S6,  * 23.2 versions before 23.2R2-S3,  * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R1-S2, 24.2R2.
CVSS 4.4 (MEDIUM) KEV: KNOWN CATALOG

Attention and evidence

HYPE SCORE
0.0/10
REALITY · THREAT PRIORITY
7.7/10
General review priority; not probability

Evidence confidence: Exploitation recorded

Why this priority?
  • Recorded exploitation baseline: +7.00
  • Technical severity: CVSS 4.4: +0.66
  • Fresh EPSS: 1.75%: +0.01

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 11 documents and public datasets.

Hype components

Headline sample (25%)
0/100
Press, 30 days (60%)
0/100
Grounded branding (15%)
0/100
HYPE TOTAL0/100

Sources and documents

Cybersecurity Dive
Press · 06 Mar 2026, 08:00 · Nearly half of exploited zero-day flaws target enterprise-grade technology - Cybersecurity Dive
Google Cloud
Press · 05 Mar 2026, 08:00 · Look What You Made Us Patch: 2025 Zero-Days in Review - Google Cloud
The Record from Recorded Future News
Press · 05 Mar 2026, 08:00 · Google says 90 zero-days exploited in 2025 as commercial vendor activity grows - The Record from Recorded Future News
CSO Online
Press · 20 Oct 2025, 07:00 · Network security devices endanger orgs with ’90s era flaws - CSO Online
www.trendmicro.com
Press · 28 Jul 2025, 07:00 · Revisiting UNC3886 Tactics to Defend Against Present Risk - www.trendmicro.com
See all 11 source documents
Field Effect
Press · 13 Mar 2025, 07:00 · China-linked threat actor deploys backdoors, rootkits on Junos OS routers - Field Effect
BleepingComputer
Press · 13 Mar 2025, 07:00 · Juniper patches bug that let Chinese cyberspies backdoor routers - BleepingComputer
Google Cloud
Press · 12 Mar 2025, 07:00 · Ghost in the Router: China-Nexus Espionage Actor UNC3886 Targets Juniper Routers - Google Cloud
Cybersecurity Dive
Press · 12 Mar 2025, 07:00 · Juniper MX routers targeted by China-nexus threat group using custom backdoors - Cybersecurity Dive
Dark Reading
Press · 12 Mar 2025, 07:00 · China-Backed Hackers Backdoor US Carrier-Grade Juniper Routers - Dark Reading
The Hacker News
Press · 12 Mar 2025, 07:00 · Chinese Hackers Breach Juniper Networks Routers With Custom Backdoors and Rootkits - The Hacker News

Score evolution

● Hype   ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.0 · reality 7.7 (2026-11-02 15:13). The curve appears once the score changes.

Public exploit evidence

0

Public exploit entries / repo candidates

Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.

Evidence in context

Confidence in exploitation evidence
Exploitation recorded
Priority basis
Recorded exploitation; CVSS 4.4; EPSS 1.7%
Attention, last 30 days
0 distinct story titles; 0 press documents; 0 publisher domains.
Technical potential
local access, high privileges, no user interaction.
Observed activity
Exploitation recorded in CISA KEV.
Known scale
Not quantified.
Evidence confidence basis
Trusted exploitation confirmation

Score evaluated: 2026-11-05 13:59:29.589072+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline
First press mention
12 Mar 2025, 07:00
Published
12 Mar 2025, 13:59
Added to the CISA KEV catalog
13 Mar 2025, 00:00
Latest press mention
06 Mar 2026, 08:00
Score calculated
05 Nov 2026, 13:59