Stack-based buffer overflow in Juniper Junos OS - CVE-2026-21903

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Main Vulnerability Database Vulnerabilities #VU121676

Stack-based buffer overflow in Juniper Junos OS - CVE-2026-21903

Published: January 20, 2026


Vulnerability identifier: #VU121676
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-21903
CWE-ID: CWE-121
Exploitation vector: Remote access
Exploit availability: No public exploit available
Vendor: Juniper Networks, Inc.
Affected software:
Juniper Junos OS

Detailed vulnerability description

The vulnerability allows a remote user to perform a denial of service attack.

The vulnerability exists due to a boundary error in the Packet Forwarding Engine (pfe). A remote user can subscribe to telemetry sensors at scale, trigger a stack-based buffer overflow and perform a denial of service attack.


How to mitigate CVE-2026-21903

Install updates from vendor's website.

Sources