CVE-2026-21901: 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 deacti

mediumCVSS 4.4CVE-2026-21901

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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 4.4
Published: 2026-07-09
Last updated: 2026-07-10
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-21901

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-219010.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-21901	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[NEW] [high] Juniper JUNOS and JUNOS Evolved: Multiple vulnerabilitiescert-bund
unknownJuniper Junos OS Multiple Vulnerabilitieshkcert
unknownMultiple vulnerabilities in Juniper Networks products (July 09, 2026)cert-fr-avis

Recent advisories for A NULL Pointer

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-60109: Zeek before 8.0.9 contains a null pointer dereference vulnerability in its Kerberos protocol a…nvd · 2026-07-09
unknownCVE-2026-56288: GNU patch is vulnerable to a NULL pointer dereference when processing a specially crafted unif…nvd · 2026-07-09
mediumCVE-2026-50812: A NULL pointer dereference in the SQLite Session Extension in SQLite 3.53.1 and SQLite trunk b…nvd · 2026-07-08
mediumCVE-2026-56401: Wazuh wazuh-modulesd before 5.0.0-beta3 contains a null pointer dereference vulnerability in i…nvd · 2026-07-08
mediumCVE-2026-50810: A NULL pointer dereference in smooth_parse_stream_index() in src/media_tools/mpd.c in GPAC mas…nvd · 2026-07-07
mediumGHSA-hwpq-hmq9-wj77: ONNX has Null Pointer Dereference in Upsample Version Converter Adapter (Zero Inputs)ghsa · 2026-07-07