CVE-2026-107635 in Dislocker
Summary
by MITRE • 10/08/2026
Dislocker through 0.7.3 contains an integer underflow vulnerability in get_vmk() and get_fvek() that allows attackers to trigger out-of-bounds heap reads via crafted datum sizes. Attackers can supply a malicious BitLocker volume image with a datum_size smaller than the 36-byte AES-CCM header, causing hexdump() to over-read and crash dislocker.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability identified in Dislocker versions through 0.7.3 represents a critical memory safety flaw rooted in improper validation of input data sizes within the functions responsible for retrieving Volume Master Keys (VMK) and Full Encryption Volume Keys (FEVK). This integer underflow condition arises when the software processes metadata from BitLocker volume images, specifically during the parsing of datum structures that define key material. The core technical failure lies in the lack of rigorous boundary checks before arithmetic operations or memory allocation decisions are made based on these sizes. When an attacker supplies a crafted BitLocker image where the specified datum_size is artificially small—specifically smaller than the 36-byte AES-CCM header required for decryption—the internal logic fails to account for this discrepancy correctly, leading to miscalculated buffer boundaries and subsequent memory access violations.
From a technical perspective, the exploitation of this vulnerability involves manipulating the datum_size field within the volume image structure. Dislocker relies on these size parameters to determine how much data to read from the heap into temporary buffers for processing. Because the validation logic does not ensure that the requested size is sufficient to contain the expected cryptographic header and payload, the application proceeds with an underflowed or incorrectly calculated length value. This leads directly to out-of-bounds heap reads when the hexdump function attempts to process the data. The hexdump utility, often used for debugging or logging purposes within such tools, iterates over memory regions based on these flawed size indicators, causing it to read beyond the allocated buffer limits into adjacent heap memory segments that may contain sensitive information or other application state.
The operational impact of this vulnerability is primarily characterized by denial of service and potential information disclosure through crash-induced core dumps or log outputs. By triggering an out-of-bounds read, attackers can cause Dislocker to terminate unexpectedly, disrupting any automated processes relying on the tool for disk decryption or forensic analysis. While the primary manifestation described is a crash, heap over-reads inherently carry the risk of leaking sensitive data stored in adjacent memory locations, such as encryption keys, user credentials, or other private information processed by the application prior to the vulnerability trigger. This makes the issue particularly severe in environments where Dislocker is used for security auditing or incident response, as it could inadvertently expose critical forensic artifacts during a compromised execution flow.
This flaw aligns with Common Weakness Enumeration (CWE) categories such as CWE-190 Integer Overflow or Wrap Around and CWE-787 Out-of-bounds Read. The exploitation technique mirrors patterns found in the MITRE ATT&CK framework, specifically relating to resource exhaustion via denial of service techniques and potentially information discovery through memory scraping if the crash behavior allows for data exfiltration before termination. Mitigation strategies must focus on rigorous input validation at the point where datum_size is parsed from the BitLocker image metadata. Developers should implement explicit checks to ensure that all size parameters are greater than or equal to the minimum required header sizes, such as the 36-byte AES-CCM structure mentioned in the vulnerability description. Additionally, employing static analysis tools and fuzzing techniques during development can help identify similar boundary condition errors before they reach production environments. Users of Dislocker should immediately update to patched versions that include these validation fixes or avoid processing untrusted BitLocker images until a secure version is available.