I'm going to assume it's an ISE appliance. Log into the appliance CLI and do show disks. This should show the areas and % used. As I've had the same before, I'm betting you will see a crashdump folder that is 100%. you should be able to go into it and delete the files so long as you don't need to see them.
This is my output, but I haven't had a crash so no folder.
ise1/admin# show disks
Internal filesystems:
/dev : 0% used ( 0 of 49035504)
/dev/shm : 1% used ( 84 of 49051952)
/run : 1% used ( 1768 of 49051952)
/sys/fs/cgroup : 0% used ( 0 of 49051952)
/ : 16% used ( 3663844 of 25571108)
/storedconfig : 2% used ( 1589 of 95054)
/opt : 18% used ( 186074164 of 1113344432)
/boot : 16% used ( 145932 of 991512)
/tmp : 2% used ( 20712 of 1983056)
/boot/efi : 3% used ( 7072 of 276312)
/run/user/440 : 0% used ( 0 of 9810388)
/opt/podman/containers/storage/overlay-containers/dd92a44577322e927c56d67469be46fd93a003ab445de3a264a7972b28f7f893/userdata/shm : 0% used ( 0 of 64000)
/opt/podman/containers/storage/overlay/725dec3aa34e116f369f0ccde0d2cd4ad7f7f2430baaf4ae6653b0862aafbeaa/merged : 18% used ( 186074164 of 1113344432)
/opt/podman/containers/storage/overlay-containers/60928c76384a71ab823c4a1042bd8700838bf40fb0d2447b9c571c2879ed7b47/userdata/shm : 1% used ( 8 of 64000)
/opt/podman/containers/storage/overlay/6e771ca40d3bc8f5acf4a31297546021ac83583b03cfda211ad57c6264dad233/merged : 18% used ( 186074164 of 1113344432)
/run/user/301 : 0% used ( 0 of 9810388)
/opt/podman/containers/storage/overlay-containers/e7317809bdcde4536ef80d390b8ae4c849921a68a41ccd8a93ec952cfd39a018/userdata/shm : 0% used ( 0 of 64000)
/opt/podman/containers/storage/overlay/28a39cda49e6ebcbb92d2374e78ba0a1c0b17124032974b0b65fe7b5d5f32a69/merged : 18% used ( 186074164 of 1113344432)
/run/user/321 : 0% used ( 0 of 9810388)
/run/user/0 : 0% used ( 0 of 9810388)
/run/user/304 : 0% used ( 0 of 9810388)
/run/user/322 : 0% used ( 0 of 9810388)
/run/user/300 : 0% used ( 0 of 9810388)
all internal filesystems have sufficient free space
ise1/admin#
