An Improper Preservation of Consistency Between Independent Representations of Shared State vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS allows a locally authenticated attacker with low privileges to cause a Denial of Service (DoS). If the device is very busy for example while executing a series of show commands on the CLI one or more SFPs might not be detected anymore. The system then changes its state to "unplugged" which is leading to traffic impact and at least a partial DoS. Once the system is less busy the port states return to their actual value. Indicators of compromise are log messages about unplugged SFPs and corresponding syspld messages without any physical or environmental cause. These can be checked by issuing the following commands: user@device# show log messages | match unplugged %PFE-6: fpc0 sfp-0/1/2 SFP unplugged %PFE-6: fpc0 sfp-0/1/3 SFP unplugged The following log messages will also be seen when this issue happens: fpc0 Error tvp_drv_syspld_read: syspld read failed for address <address> fpc0 Error[-1]:tvp_optics_presence_get - Syspld read failed for port <pic/port> fpc0 optics pres failed(-1) for pic <pic> port <port> fpc0 tvp_drv_syspld_read: i2c access retry count 200 This issue affects Juniper Networks Junos OS on EX2300 Series, EX3400 Series: All versions prior to 18.4R3-S11; 19.1 versions prior to 19.1R3-S9; 19.2 versions prior to 19.2R1-S9, 19.2R3-S5; 19.3 versions prior to 19.3R3-S6; 19.4 versions prior to 19.4R2-S7, 19.4R3-S8; 20.1 versions prior to 20.1R3-S4; 20.2 versions prior to 20.2R3-S4; 20.3 versions prior to 20.3R3-S4; 20.4 versions prior to 20.4R3-S3; 21.1 versions prior to 21.1R3-S1; 21.2 versions prior to 21.2R3; 21.3 versions prior to 21.3R2; 21.4 versions prior to 21.4R2.