Junos OS and Junos OS Evolved: /var/run/<pid>.env files are potentially not deleted during termination of a gRPC connection causing inode exhaustion

Summary

A Missing Release of File Descriptor or Handle after Effective Lifetime vulnerability in plugable authentication module (PAM) of Juniper Networks Junos OS and Junos OS Evolved allows a locally authenticated attacker with low privileges to cause a Denial of Service (DoS). It is possible that after the termination of a gRPC connection the respective/var/run/<pid>.env file is not getting deleted which if occurring repeatedly can cause inode exhaustion. Inode exhaustion can present itself in two different ways: 1. The following log message can be observed: host kernel: pid <pid> (<process>), uid <uid> inumber <number> on /.mount/var: out of inodes which by itself is a clear indication. 2. The following log message can be observed: host <process>[<pid>]: ... : No space left on device which is not deterministic and just a representation of a write error which could have several reasons. So the following check needs to be done: user@host> show system storage no-forwarding Filesystem Size Used Avail Capacity Mounted on /dev/ada1p1 475M 300M 137M 69% /.mount/var which indicates that the write error is not actually due to a lack of disk space. If either 1. or 2. has been confirmed, then the output of: user@host> file list /var/run/*.env | count need to be checked and if it indicates a high (>10000) number of files the system has been affected by this issue. This issue affects: Juniper Networks Junos OS All versions prior to 19.1R3-S8; 19.2 versions prior to 19.2R3-S6; 19.3 versions prior to 19.3R3-S5; 19.4 versions prior to 19.4R2-S6, 19.4R3-S7; 20.1 version 20.1R1 and later versions; 20.2 versions prior to 20.2R3-S5; 20.3 versions prior to 20.3R3-S4; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2. Juniper Networks Junos OS Evolved All versions prior to 20.4R3-EVO; 21.1 versions prior to 21.1R3-S1-EVO; 21.2 versions prior to 21.2R1-S1-EVO, 21.2R2-EVO.