buffer overruns in libfsimage iso9660 handling

[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]

The directory and Rock Ridge / SUSP walk in libfsimage's iso9660 driver
derives several lengths directly from attacker-controlled on-disk fields
without validating them:

* The directory loop itself assumes a good record length. This is
CVE-2026-42494.

* The calculation of the System Use area may underflow. This is
CVE-2026-42495.

* The Rock Ridge extension loop assumes a good (inner) record length.
This is CVE-2026-62423.

* The Rock Ridge NM record processing assumes a good entry length.
This is CVE-2026-62424.

* The Rock Ridge CE record processing assumes a good size and offset.
This is CVE-2026-62425.