Answer in brief
CVE-2026-21901 records a Medium severity (CVSS 4.4) vulnerability in Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash. The current sources do not mark it as known exploited. The current feed maps Juniper Networks/Junos OS (generic), Juniper Networks/Junos OS Evolved (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Juniper Networks/Junos OS (generic), Juniper Networks/Junos OS Evolved (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Juniper Networks/Junos OSgeneric | >=22.3 <22.3R3-S5 || >=22.4 <22.4R3-S10 || >=23.2 <23.2R2-S7 || >=23.4 <23.4R2-S8 | 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8 |
| Juniper Networks/Junos OS Evolvedgeneric | >=23.2 <23.2R2-S7-EVO || >=23.4 <23.4R2-S8-EVO | 23.2R2-S7-EVO, 23.4R2-S8-EVO |
Published upstream
Jul 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 10, 2026
A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged attacker setting or deactivating a specific SSH configuration parameter to create a Denial of Service (DoS). A local high-privileged user configuring or deactivating a specific 'system services ssh' configuration parameter can exploit a null pointer dereference in one of the functions used by SSH. The function attempts to dereference a null pointer when accessing certain configuration data, resulting in an mgd process crash and restart. Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition. This issue affects: Junos OS: * from 22.3 before 22.3R3-S5; * from 22.4 before 22.4R3-S10; * from 23.2 before 23.2R2-S7; * from 23.4 before 23.4R2-S8. This issue does not affect Junos OS before 22.3R1. Junos OS Evolved: * from 22.3R1-EVO before 23.2R2-S7-EVO; * from 23.4 before 23.4R2-S8-EVO. This issue does not affect Junos OS Evolved before 22.3R1-EVO.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-21901 records a Medium severity (CVSS 4.4) vulnerability in Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash. The current sources do not mark it as known exploited. The current feed maps Juniper Networks/Junos OS (generic), Juniper Networks/Junos OS Evolved (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Juniper Networks/Junos OS (generic), Juniper Networks/Junos OS Evolved (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Juniper Networks/Junos OSgeneric | >=22.3 <22.3R3-S5 || >=22.4 <22.4R3-S10 || >=23.2 <23.2R2-S7 || >=23.4 <23.4R2-S8 | 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8 |
| Juniper Networks/Junos OS Evolvedgeneric | >=23.2 <23.2R2-S7-EVO || >=23.4 <23.4R2-S8-EVO | 23.2R2-S7-EVO, 23.4R2-S8-EVO |
Published upstream
Jul 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 10, 2026
A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged attacker setting or deactivating a specific SSH configuration parameter to create a Denial of Service (DoS). A local high-privileged user configuring or deactivating a specific 'system services ssh' configuration parameter can exploit a null pointer dereference in one of the functions used by SSH. The function attempts to dereference a null pointer when accessing certain configuration data, resulting in an mgd process crash and restart. Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition. This issue affects: Junos OS: * from 22.3 before 22.3R3-S5; * from 22.4 before 22.4R3-S10; * from 23.2 before 23.2R2-S7; * from 23.4 before 23.4R2-S8. This issue does not affect Junos OS before 22.3R1. Junos OS Evolved: * from 22.3R1-EVO before 23.2R2-S7-EVO; * from 23.4 before 23.4R2-S8-EVO. This issue does not affect Junos OS Evolved before 22.3R1-EVO.
Quoted source text, attributed separately from HOL analysis.