Security readout for executives and security teams
Plain-English summary
CVE-2026-21913 can make certain Juniper EX4000 48-port switches crash and restart when they receive a high volume of traffic aimed at the device itself. This creates a full service outage until the switch automatically restarts. The issue is unauthenticated and network-reachable, so exposed management or device-facing interfaces increase business risk.
Executive priority
Prioritize remediation for affected switches supporting critical networks, data centers, or high-availability paths. This is a denial-of-service issue, not a disclosed data theft issue, but outages could be material if these switches carry production traffic.
Technical view
Juniper describes an Incorrect Initialization of Resource flaw in Junos OS Internal Device Manager on EX4000-48T, EX4000-48P, and EX4000-48MP. A high volume of traffic destined to the device can crash and restart the FXPC. Affected releases are 24.4 before 24.4R2 and 25.2 before 25.2R1-S2 or 25.2R2. CVSS v4.0 score is 8.7.
Likely exposure
Organizations using EX4000 48-port models on affected Junos OS releases are exposed. The sources do not indicate impact to EX4000 models outside EX4000-48T, EX4000-48P, or EX4000-48MP, and versions before 24.4R1 are stated as unaffected because EX4000 support began at 24.4R1.
Exploitation context
The attack is network-based, unauthenticated, and requires high-volume traffic directed at the device. The reported impact is denial of service through FXPC crash and restart. The source bundle does not report active exploitation, and the CVE is not marked in KEV.
Researcher notes
The evidence is limited to CVE and Juniper advisory details in the provided bundle. No public exploit status, workaround beyond upgrading, or broader product impact is cited. Validate exact model and release before assessing exposure.
Mitigation direction
- Upgrade affected EX4000-48T, EX4000-48P, and EX4000-48MP devices to a fixed Junos OS release.
- For 24.4 deployments, move to 24.4R2 or later per Juniper guidance.
- For 25.2 deployments, move to 25.2R1-S2, 25.2R2, or later per Juniper guidance.
- Restrict unnecessary traffic destined to switch control or management interfaces where operationally feasible.
- Monitor Juniper advisory JSA106014 for any updated workaround or release guidance.
Validation and detection
- Inventory EX4000 48-port models and record current Junos OS versions.
- Confirm whether any devices run 24.4 before 24.4R2 or 25.2 before fixed releases.
- Review device logs for the documented watchdog panic and core dump reboot reason.
- Check for recent unexplained FXPC crashes, restarts, or full switch service outages.
- Verify remediated devices report a fixed Junos OS version after upgrade.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1419: Exact CWE lookup
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Open ATT&CK lookupCVE-2026-21913 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.7 (4.0)
- Known Exploited
- No
- Published
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/AU:Y/R:A/RE:M
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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/AU:Y/R:A/RE:M——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.7HighVector: 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/AU:Y/R:A/RE:M
Source materials
- CVE List V5 sourceCVE List V5
- https://supportportal.juniper.net/JSA106014CVE reference · vendor-advisory
- https://kb.juniper.net/JSA106014CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Incorrect Initialization of Resource
Incorrect Initialization of Resource represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.