CVE-2026-21901
Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
Description
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.
INFO
Published Date :
July 9, 2026, 9:16 p.m.
Last Modified :
July 9, 2026, 9:16 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-21901
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Junos OS to a fixed version.
- Update Junos OS Evolved to a fixed version.
- Apply vendor-supplied patches or updates.
- Restrict configuration access to authorized personnel.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-21901.
| URL | Resource |
|---|---|
| https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6 | |
| https://supportportal.juniper.net/JSA110072 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-21901 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-21901
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-21901 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-21901 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Juniper Networks', 'product': 'Junos OS', 'versions': [{'status': 'affected', 'version': '22.3', 'lessThan': '22.3R3-S5', 'versionType': 'custom'}, {'status': 'affected', 'version': '22.4', 'lessThan': '22.4R3-S10', 'versionType': 'custom'}, {'status': 'affected', 'version': '23.2', 'lessThan': '23.2R2-S7', 'versionType': 'custom'}, {'status': 'affected', 'version': '23.4', 'lessThan': '23.4R2-S8', 'versionType': 'custom'}, {'status': 'unaffected', 'version': '0', 'lessThan': '22.3R1', 'versionType': 'custom'}], 'defaultStatus': 'unaffected'}, {'vendor': 'Juniper Networks', 'product': 'Junos OS Evolved', 'versions': [{'status': 'affected', 'version': '23.2', 'lessThan': '23.2R2-S7-EVO', 'versionType': 'custom'}, {'status': 'affected', 'version': '23.4', 'lessThan': '23.4R2-S8-EVO', 'versionType': 'custom'}, {'status': 'unaffected', 'version': '0', 'lessThan': '22.3R1-EVO', 'versionType': 'custom'}], 'defaultStatus': 'unaffected'}] Added Description 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. Added CVSS V4.0 AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/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:Y/R:A/V:D/RE:M/U:Green Added CVSS V3.1 AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-476 Added Reference https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6 Added Reference https://supportportal.juniper.net/JSA110072