CVE-2026-42495 in libfsimage
Summary
by MITRE • 07/28/2026
[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.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerabilities described in this CVE information record represent critical flaws within the libfsimage library's iso9660 driver implementation that collectively expose systems to potential denial of service and arbitrary code execution attacks. These issues arise from insufficient validation of attacker-controlled on-disk fields during directory and Rock Ridge extension processing, creating multiple pathways for malicious actors to manipulate file system parsing routines. The vulnerabilities specifically target the ISO 9660 file system implementation which is widely used in optical media and various storage systems, making them particularly dangerous due to the widespread adoption of this standard.
The primary technical flaw manifests in the directory traversal logic where the driver assumes valid record lengths without proper validation checks, creating CVE-2026-42494. This fundamental assumption allows attackers to craft malformed directory entries that can cause infinite loops or buffer overflows during file system parsing. The second vulnerability CVE-2026-42495 occurs in the System Use area calculation where underflow conditions can be triggered by manipulating on-disk fields, potentially leading to memory corruption or system crashes. These core parsing issues are amplified by additional vulnerabilities in the Rock Ridge extension processing, which implements similar flawed assumptions about record lengths and field values.
The Rock Ridge extension processing contains several interconnected vulnerabilities that demonstrate the scope of the problem. CVE-2026-62423 addresses the extension loop that assumes valid inner record lengths without validation, while CVE-2026-62424 targets the NM (Name) record processing that assumes proper entry length values. The most complex vulnerability CVE-2026-62425 affects CE (Continuation Entry) record processing where both size and offset fields are assumed to be valid without proper bounds checking. These vulnerabilities collectively represent a pattern of insufficient input validation that can be exploited through carefully crafted ISO 9660 file system structures, potentially allowing attackers to execute arbitrary code or cause system instability.
The operational impact of these vulnerabilities extends beyond simple denial of service scenarios, as they create opportunities for privilege escalation and remote code execution in systems that process untrusted ISO images. The CWE classification for these issues would likely fall under CWE-129 Input Validation and CWE-191 Integer Underflow/Overflow, with potential mappings to CWE-787 Out-of-bounds Write when memory corruption occurs. From an ATT&CK perspective, these vulnerabilities map to techniques involving privilege escalation through software vulnerabilities and denial of service attacks targeting system resources. The exploitation requires minimal privileges since the attacks target file system parsing components that are typically invoked during normal system operations.
Mitigation strategies should focus on implementing comprehensive input validation throughout the iso9660 driver, particularly in all record length calculations and field value processing. Systems should enforce strict bounds checking on all attacker-controlled fields before any processing occurs, with proper error handling for malformed entries. The implementation should include defensive programming practices such as maximum length limits on directory entries, overflow detection in arithmetic operations, and comprehensive testing of edge cases. Organizations should also consider implementing sandboxing mechanisms when processing untrusted ISO files and maintain updated versions of affected libraries to prevent exploitation of these vulnerabilities in production environments.