Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2025-21589 is a critical-severity Authentication Bypass Using an Alternate Path or Channel (CWE-288) vulnerability in Juniper Networks Session (inferred from references). Its CVSS base score is 9.3 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 28% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-21589 is an Authentication Bypass Using an Alternate Path or Channel vulnerability (CWE-288) affecting Juniper Networks Session Smart Router, Session Smart Conductor, and WAN Assurance Managed Routers. The issue impacts versions from 5.6.7 before 5.6.17; from 6.0 before 6.0.8 (affected from 6.0.8); from 6.1 before 6.1.12-lts; from 6.2 before 6.2.8-lts; and from 6.3 before 6.3.3-r2 across all three products. Published on 2026-01-27, it has a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity.
A network-based attacker with no privileges or user interaction can exploit this vulnerability to bypass authentication mechanisms and gain administrative control of the affected device. Successful exploitation provides high confidentiality, integrity, and availability impacts, potentially allowing full compromise of the router, conductor, or managed router.
Juniper's security advisory at https://kb.juniper.net/JSA94663 details the issue and recommends upgrading to fixed versions such as 5.6.17, 6.0.8, 6.1.12-lts, 6.2.8-lts, or 6.3.3-r2. Additional support resources include the end-of-life software page at https://support.juniper.net/support/eol/software/ssr/ and the support portal at https://supportportal.juniper.net/.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-206381
Vulnerability Data
An Authentication Bypass Using an Alternate Path or Channel vulnerability in Juniper Networks Session Smart Router may allows a network-based attacker to bypass authentication and take administrative control of the device. This issue affects Session Smart Router: * from 5.6.7…
more
before 5.6.17, * from 6.0 before 6.0.8 (affected from 6.0.8), * from 6.1 before 6.1.12-lts, * from 6.2 before 6.2.8-lts, * from 6.3 before 6.3.3-r2; This issue affects Session Smart Conductor: * from 5.6.7 before 5.6.17, * from 6.0 before 6.0.8 (affected from 6.0.8), * from 6.1 before 6.1.12-lts, * from 6.2 before 6.2.8-lts, * from 6.3 before 6.3.3-r2; This issue affects WAN Assurance Managed Routers: * from 5.6.7 before 5.6.17, * from 6.0 before 6.0.8 (affected from 6.0.8), * from 6.1 before 6.1.12-lts, * from 6.2 before 6.2.8-lts, * from 6.3 before 6.3.3-r2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 7 hardening rules · 3 OS baselines
V6.4.3V6.6.1V12.1.3
Mitigating Controls (NIST 800-53 r5) AI
Requires a tamperproof, always-invoked reference monitor that structurally blocks bypass via any alternate path.
Enforces authorization checks on every logical access path, eliminating unauthenticated alternate channels.
Mandates unique identification and authentication for all organizational users, covering the primary authentication requirement.
Controls all external and key internal interfaces, reducing the chance of unauthenticated alternate channels.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Requiring authentication on every channel and path directly eliminates alternate-path bypasses.
Enforcing authorizations and least privilege across all access vectors prevents unauthenticated alternate paths.
Protecting networks and environments from unauthorized logical access blocks bypass via undocumented channels.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect alternate-path bypasses but does not prevent them in production.
Secure authentication control directly mitigates bypass by requiring strong, consistent authentication on all paths.
Access control policy directly addresses alternate authentication paths by requiring all channels to enforce authentication.
Authentication information management ensures credentials and mechanisms are consistently applied across all access paths.
Access rights provisioning and review prevent bypass via unmonitored or alternate channels.
Privileged access rights control reduces risk of bypass through elevated or alternate paths.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248598 There must be no ".shosts" files on the OL 8 operating system. prevents CWE-288
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-288
Oracle Linux 9 (2 rules)
- V-271757 OL 9 file systems must not contain shosts.equiv files. prevents CWE-288
- V-271758 OL 9 file systems must not contain .shosts files. prevents CWE-288
RHEL 7 (3 rules)
- V-204440 Red Hat Enterprise Linux operating systems version 7.2 or newer using Unified Extensible Firmware Interface (UEFI) must require authentication upon booting into single-user and maintenance modes. prevents CWE-288
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-288
- V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. prevents CWE-288