CVE-2026-40026: Sleuth Kit Buffer Overflow Vulnerability

CVE-2026-40026 Overview

CVE-2026-40026 is an out-of-bounds read vulnerability in The Sleuth Kit through version 4.14.0 that affects the ISO9660 filesystem parser. The vulnerability exists in the parse_susp() function, which processes System Use Sharing Protocol (SUSP) entries from disk images. The function trusts the len_id, len_des, and len_src fields from the disk image to memcpy data into a stack buffer without verifying that the source data falls within the parsed SUSP block boundaries.

An attacker can craft a malicious ISO image that causes reads past the end of the SUSP data buffer. Additionally, a zero-length SUSP entry can trigger an infinite parsing loop, resulting in a denial of service condition.

Critical Impact

Attackers can exploit this vulnerability through specially crafted ISO disk images to cause out-of-bounds memory reads and potentially trigger infinite loops, affecting forensic analysis workflows that rely on The Sleuth Kit.

Affected Products

• The Sleuth Kit through version 4.14.0
• Applications and forensic tools that incorporate The Sleuth Kit's ISO9660 parser
• Digital forensics workflows processing untrusted ISO disk images

Discovery Timeline

• 2026-04-08 - CVE-2026-40026 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-40026

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read). The parse_susp() function in the ISO9660 filesystem parser processes SUSP extension records found within Rock Ridge extensions in ISO9660 images. These records contain length fields that specify the size of various data components within each entry.

The root issue is that the parsing function implicitly trusts the length values read directly from the disk image without adequate boundary validation. When processing SUSP entries, the code would read beyond the allocated buffer boundaries if a malicious image specified length values larger than the actual available data.

A secondary issue arises with zero-length entries. If an attacker provides a SUSP entry with a length of zero, the parsing loop would not advance the buffer pointer, causing an infinite loop condition that would hang the application.

Root Cause

The root cause is insufficient input validation in the SUSP parsing routine. The parse_susp() function uses attacker-controlled length fields (len_id, len_des, len_src) from untrusted disk image data to determine how much data to copy without properly validating that:

1. The specified lengths do not exceed the remaining buffer space
2. The entry length is non-zero, ensuring the parser makes forward progress

This trust of disk-supplied values is problematic because forensic tools are specifically designed to analyze potentially malicious or corrupted disk images.

Attack Vector

The attack requires local access where a user or automated process must open a maliciously crafted ISO image with The Sleuth Kit or an application that uses its libraries. The attacker must convince a user to analyze the malicious image or place it where automated forensic pipelines will process it.

Exploitation scenarios include:

• Targeting forensic analysts who receive ISO images for examination
• Compromising automated malware analysis sandboxes that use The Sleuth Kit
• Affecting backup verification systems that parse ISO archives

    while ((uintptr_t)buf + sizeof(iso9660_susp_head) <= (uintptr_t)end) {
        iso9660_susp_head *head = (iso9660_susp_head *) buf;

-        if (buf + head->len - 1 > end)
+        if ((buf + head->len - 1 > end) || (head->len == 0))
            break;

        /* Identify the entry type -- listed in the order

Source: GitHub Commit Update

The patch adds a check for zero-length entries (head->len == 0), ensuring the parsing loop terminates when encountering invalid entries that would otherwise cause infinite iteration.

Detection Methods for CVE-2026-40026

Indicators of Compromise

• Unexpected application hangs or high CPU usage when processing ISO images with The Sleuth Kit tools
• Application crashes or segmentation faults during ISO9660 filesystem analysis
• Unusual memory access patterns in forensic tool processes

Detection Strategies

• Monitor for abnormal resource consumption when The Sleuth Kit processes ISO images
• Implement file integrity monitoring on ISO images before forensic processing
• Deploy endpoint detection to identify crash patterns in tsk binary executions
• Use SentinelOne's behavioral AI to detect anomalous process behavior during disk image analysis

Monitoring Recommendations

• Enable verbose logging for forensic analysis workflows to capture parsing failures
• Implement timeout mechanisms for automated ISO processing pipelines
• Monitor memory usage patterns in applications using The Sleuth Kit libraries

How to Mitigate CVE-2026-40026

Immediate Actions Required

• Update The Sleuth Kit to a version containing the security patch referenced in commit a95b0ac21733b059a517aaefa667a17e1bcbdee1
• Review automated forensic pipelines that process untrusted ISO images
• Implement additional sandboxing for ISO image analysis workflows
• Consider preprocessing ISO images with file validation checks before analysis

Patch Information

The vulnerability has been addressed in The Sleuth Kit codebase. The fix adds validation for zero-length SUSP entries to prevent infinite loops and ensures proper boundary checking. Details are available in GitHub Pull Request #3445 and the security commit.

For additional technical details, refer to the VulnCheck Advisory for Sleuth Kit.

Workarounds

• Isolate The Sleuth Kit processes in sandboxed environments when analyzing untrusted images
• Implement process timeouts to automatically terminate hung parsing operations
• Use memory-safe wrappers or containers to limit the impact of out-of-bounds reads
• Perform preliminary validation of ISO images using alternative tools before detailed analysis

# Configuration example: Running The Sleuth Kit in a timeout-controlled environment
# Set a timeout to prevent infinite loop conditions
timeout 300 fls -r /path/to/untrusted.iso

# Alternative: Run analysis in a containerized environment with resource limits
docker run --rm --memory="512m" --cpus="1" sleuthkit-container fls -r /mnt/image.iso