CVE-2025-21594

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2025-04-09. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading to Denial of Service (DoS).

In a DS-Lite (Dual-Stack Lite) and NAT (Network Address Translation) scenario, when crafted IPv6 traffic is received and prefix-length is set to 56, the ports assigned to the user will not be freed.  Eventually, users cannot establish new connections. Affected FPC/PIC need to be manually restarted to recover. Following is the command to identify the issue: 

    user@host> show services nat source port-block      Host_IP                     External_IP                   Port_Block      Ports_Used/       Block_State/                                                               Range           Ports_Total       Left_Time(s)     2001::                        x.x.x.x                     58880-59391     256/256*1         Active/-       >>>>>>>>port still usedThis issue affects Junos OS on MX Series: 

* from 21.2 before 21.2R3-S8,  * from 21.4 before 21.4R3-S7,  * from 22.1 before 22.1R3-S6,  * from 22.2 before 22.2R3-S4,  * from 22.3 before 22.3R3-S3,  * from 22.4 before 22.4R3-S2,  * from 23.2 before 23.2R2-S1,  * from 23.4 before 23.4R1-S2, 23.4R2.

This issue does not affect versions before 20.2R1.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
32.6%
KEV
Not listed

Published

April 9, 2025

Last Modified

January 26, 2026

References (1)

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 02:50 UTCEG score recompute
  2. 2026-07-22 14:07 UTCEPSS rescore
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  62. 2026-05-30 07:43 UTCEG score recompute
  63. 2026-05-30 07:43 UTCGHSA enrichment
  64. 2026-05-29 13:44 UTCEPSS rescore

Frequently asked(5)

What is CVE-2025-21594?
CVE-2025-21594 is a high vulnerability published on April 9, 2025. An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading to Denial of Service (DoS). In a DS-Lite (Dual-Stack Lite) and NAT (Network Address Translation)…
When was CVE-2025-21594 disclosed?
CVE-2025-21594 was first published in the National Vulnerability Database on April 9, 2025, with the most recent update on January 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-21594 actively exploited?
CVE-2025-21594 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 32.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-21594?
CVE-2025-21594 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2025-21594?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-21594, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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