CVE-2021-31364

CVE-2021-31364 is a denial-of-service vulnerability affecting Juniper Networks Junos OS on specific SRX Series firewalls (SRX300, SRX500, SRX1500, and SRX5000 with SPC2). It stems from a race condition and improper check in the flow daemon (flowd) that can be triggered by unauthenticated attackers sending specific traffic when session-close logging is configured. The vulnerability has a CVSS score of 5.9 (Medium) due to its network-based attack vector, high attack complexity, and high impact on availability, as it can cause a sustained crash of the traffic forwarding process. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.