Incorrect calculation in Junos OS Evolved - CVE-2026-21911
Published: January 20, 2026
Vulnerability identifier: #VU121700
CSH Severity: Medium
CVSS v4: 7.1 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21911
CWE-ID: CWE-682
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to incorrect calculation error in the Layer 2 Control Protocol Daemon (l2cpd). A remote non-authenticated attacker can cause the learning of new MACs over label-switched interfaces (LSI) to stop while generating a flood of logs, resulting in high CPU usage.
Affected software
Junos OS Evolved
How to mitigate CVE-2026-21911
Install updates from vendor's website.
Junos OS Evolved - addressed in versions 21.4R3-S7-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO, 23.4R2-EVO, 24.2R1-EVO