CVE-2026-21913
Juniper Junos 24.4 … 25.2
Raw 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/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:A/V:X/RE:M/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-2026-21913 is a high-severity Improper Initialization (CWE-665) vulnerability in Juniper Junos. Its CVSS base score is 8.7 (High).
Operationally, ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — 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-2026-21913 is an Incorrect Initialization of Resource vulnerability (CWE-665) in the Internal Device Manager (IDM) of Juniper Networks Junos OS on EX4000 switch models. It affects the 48-port variants, including EX4000-48T, EX4000-48P, and EX4000-48MP, running Junos OS versions 24.4 prior to 24.4R2 and 25.2 prior to 25.2R1-S2 or 25.2R2. A high volume of traffic destined to the device triggers an FXPC crash and restart, resulting in a complete service outage until the device automatically reboots. The incident is indicated by the reboot reason "0x4000002:watchdog + panic with core dump" in the output of 'show chassis routing-engine' or log messages. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
An unauthenticated, network-based attacker can exploit this vulnerability by sending a high volume of traffic to the affected device. Successful exploitation causes the FXPC process to crash, leading to a Denial-of-Service (DoS) condition with a full service outage during the restart period.
Juniper's security advisories at https://kb.juniper.net/JSA106014 and https://supportportal.juniper.net/JSA106014 detail the affected versions and provide recommended patches or upgrades to mitigate the issue, such as Junos OS 24.4R2 and later for the 24.4 series, or 25.2R1-S2, 25.2R2, and subsequent releases for the 25.2 series. The first Junos OS release for EX4000 models was 24.4R1, so earlier versions are not impacted.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2688
Vulnerability Data
An Incorrect Initialization of Resource vulnerability in the Internal Device Manager (IDM) of Juniper Networks Junos OS on EX4000 models allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On EX4000 models with 48 ports (EX4000-48T, EX4000-48P, EX4000-48MP) a…
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high volume of traffic destined to the device will cause an FXPC crash and restart, which leads to a complete service outage until the device has automatically restarted. The following reboot reason can be seen in the output of 'show chassis routing-engine' and as a log message: reason=0x4000002 reason_string=0x4000002:watchdog + panic with core dump This issue affects Junos OS on EX4000-48T, EX4000-48P and EX4000-48MP: * 24.4 versions before 24.4R2, * 25.2 versions before 25.2R1-S2, 25.2R2. This issue does not affect versions before 24.4R1 as the first Junos OS version for the EX4000 models was 24.4R1.
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly exercises initialization paths and can reveal missing or incorrect resource setup.
Engineering principles applied during design and implementation can require explicit initialization to a known state.
Requiring the system to fail to a known state structurally reduces the chance that uninitialized resources remain reachable.
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.
Secure SDLC practices directly enforce proper resource initialization during coding and testing.
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 uninitialized variables but does not itself enforce initialization practices.
Configuration management can enforce secure defaults and initialization settings but is not the primary control for code-level initialization.
Secure development life cycle mandates initialization checks and secure defaults that directly prevent improper resource initialization.
Secure system architecture and engineering principles require explicit initialization of resources and secure state management.
Secure coding standards explicitly forbid uninitialized variables and mandate proper resource initialization before use.