title: Junos OS Evolved: PTX Series: Multiple FPCs become unreachable due to continuous polling of specific SNMP OID
description: A limitless resource allocation vulnerability in FPC resources of Juniper Networks Junos OS Evolved on PTX Series allows an unprivileged attacker to cause Denial of Service (DoS). Continuously polling the SNMP jnxCosQstatTable causes the FPC to run out of GUID space, causing a Denial of Service to the FPC resources. When the FPC runs out of the GUID space, you will see the following syslog messages. The evo-aftmand-bt process is asserting. fpc1 evo-aftmand-bt[17556]: %USER-3: get_next_guid: Ran out of Guid Space start 1748051689472 end 1752346656767 fpc1 audit[17556]: %AUTH-5: ANOM_ABEND auid=4294967295 uid=0 gid=0 ses=4294967295 pid=17556 comm="EvoAftManBt-mai" exe="/usr/sbin/evo-aftmand-bt" sig=6 fpc1 kernel: %KERN-5: audit: type=1701 audit(1648567505.119:57): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=17556 comm="EvoAftManBt-mai" exe="/usr/sbin/evo-aftmand-bt" sig=6 fpc1 emfd-fpa[14438]: %USER-5: Alarm set: APP color=red, class=CHASSIS, reason=Application evo-aftmand-bt fail on node Fpc1 fpc1 emfd-fpa[14438]: %USER-3-EMF_FPA_ALARM_REP: RaiseAlarm: Alarm(Location: /Chassis[0]/Fpc[1] Module: sysman Object: evo-aftmand-bt:0 Error: 2) reported fpc1 sysepochman[12738]: %USER-5-SYSTEM_REBOOT_EVENT: Reboot [node] [ungraceful reboot] [evo-aftmand-bt exited] The FPC resources can be monitored using the following commands: user@router> start shell [vrf:none] user@router-re0:~$ cli -c "show platform application-info allocations app evo-aftmand-bt" | grep ^fpc | grep -v Route | grep -i -v Nexthop | awk '{total[$1] += $5} END { for (key in total) { print key " " total[key]/4294967296 }}' Once the FPCs become unreachable they must be manually restarted as they do not self-recover. This issue affects Juniper Networks Junos OS Evolved on PTX Series: All versions prior to 20.4R3-S4-EVO; 21.1-EVO version 21.1R1-EVO and later versions; 21.2-EVO version 21.2R1-EVO and later versions; 21.3-EVO versions prior to 21.3R3-EVO; 21.4-EVO versions prior to 21.4R2-EVO; 22.1-EVO versions prior to 22.1R2-EVO.
problem types: Denial of Service (DoS)
affected:
{
vendor: Juniper Networks
product: Junos OS Evolved
versions:
version: unspecified, lessThan: 20.4R3-S4-EVO, status: affected, versionType: custom
version: 21.1R1-EVO, status: affected, lessThan: 21.1-EVO*, versionType: custom
version: 21.2R1-EVO, status: affected, lessThan: 21.2-EVO*, versionType: custom
version: 21.3-EVO, status: affected, lessThan: 21.3R3-EVO, versionType: custom
version: 21.4-EVO, status: affected, lessThan: 21.4R2-EVO, versionType: custom
version: 22.1-EVO, status: affected, lessThan: 22.1R2-EVO, versionType: custom
platforms: PTX Series
}
metrics:
cvssV3_1: [
version: 3.1
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: NONE
userInteraction: NONE
scope: UNCHANGED
confidentialityImpact: NONE
integrityImpact: NONE
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
]
exploits: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
solutions: The following software releases have been updated to resolve this specific issue:
Junos OS Evolved: 20.4R3-S4-EVO, 21.3R3-EVO, 21.4R2-EVO, 22.1R2-EVO, 22.2R1-EVO, and all subsequent releases.
workarounds: To apply a workaround exclude the MIB from being polled with the following configuration snippet:
[snmp view cos oid 1.3.6.1.4.1.2636.3.15.4 exclude]
[snmp community public view cos]
Additionally, disable SNMP (disabled by default), utilize edge filtering with source-address validation (uRPF, etc.), access control lists (ACLs), and/or SNMPv3 authentication to limit access to the device only from trusted hosts.
In addition to the workaround recommendations listed above, it is good security practice to limit the exploitable attack surface of critical infrastructure networking equipment. Use access lists or firewall filters to limit access to the device to only trusted networks, administrators and hosts.