Stack-based buffer overflow in Junos OS - CVE-2026-21903
Published: January 20, 2026
Vulnerability identifier: #VU121676
CSH Severity: Medium
CVSS v4: 7.1 [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]
CVE-ID: CVE-2026-21903
CWE-ID: CWE-121
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Junos OS
How to mitigate CVE-2026-21903
Install updates from vendor's website.
Junos OS - addressed in versions 22.4R3-S7, 23.2R2-S4, 23.4R2, 24.2R1