{"cve":"CVE-2025-21594","nvd":{"published":"2025-04-09T20:15:25.620","modified":"2026-06-17T08:43:48.513","status":"Analyzed","description":"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).\n\nIn 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.\nFollowing is the command to identify the issue: \n\n\n    user@host> show services nat source port-block \n    Host_IP                       External_IP                    Port_Block      Ports_Used/        Block_State/\n                                                               Range             Ports_Total        Left_Time(s)\n    2001::                        x.x.x.x                     58880-59391     256/256*1         Active/-        >>>>>>>>port still usedThis issue affects Junos OS on MX Series: \n\n  *  from 21.2 before 21.2R3-S8, \n  *  from 21.4 before 21.4R3-S7, \n  *  from 22.1 before 22.1R3-S6, \n  *  from 22.2 before 22.2R3-S4, \n  *  from 22.3 before 22.3R3-S3, \n  *  from 22.4 before 22.4R3-S2, \n  *  from 23.2 before 23.2R2-S1, \n  *  from 23.4 before 23.4R1-S2, 23.4R2.\n\n\nThis issue does not affect versions before 20.2R1.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/R:U","score":8.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-754"],"references":["https://supportportal.juniper.net/JSA96449"],"products":["juniper:junos"],"source":"nvd","synced_at":"2026-10-19T22:00:57.946988208+00:00"},"epss":{"cve":"CVE-2025-21594","score":0.00424,"percentile":0.36736,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}