Time-of-check Time-of-use (TOCTOU) Race Condition in Junos OS - CVE-2021-0289
Published: July 15, 2021
Vulnerability identifier: #VU54915
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-2021-0289
CWE-ID: CWE-367
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass implemented security restrictions.
The vulnerability exists due to a race condition between the Device Control Daemon (DCD) and firewall process (dfwd) daemons of Juniper Networks Junos OS, when user-defined ARP Policer is configured and applied on one or more Aggregated Ethernet (AE) interface units. A remote attacker on the local network can bypass the user-defined ARP Policer.
Affected software
Junos OS
How to mitigate CVE-2021-0289
Install updates from vendor's website.
Junos OS - addressed in versions 15.1R7-S10, 18.4R2-S9, 18.4R3-S9, 19.4R3-S4, 20.1R3, 20.2R3-S2, 20.4R3, 21.1R2, 21.2R1