CVE-2017-18199 in libcdio
Summary
by MITRE
realloc_symlink in rock.c in GNU libcdio before 1.0.0 allows remote attackers to cause a denial of service (NULL Pointer Dereference) via a crafted iso file.
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Analysis
by VulDB Data Team • 02/10/2023
The vulnerability identified as CVE-2017-18199 represents a critical null pointer dereference flaw within the GNU libcdio library version 0.9.10 and earlier. This issue specifically affects the realloc_symlink function located in the rock.c source file, which is responsible for handling Rock Ridge extensions in ISO 9660 filesystem images. The vulnerability arises when processing crafted ISO files that contain malformed Rock Ridge metadata, creating a scenario where the software attempts to dereference a null pointer during memory reallocation operations. This flaw demonstrates a classic buffer management error that can be exploited by remote attackers to disrupt service availability.
The technical implementation of this vulnerability stems from inadequate input validation within the ISO file parsing mechanism. When the realloc_symlink function processes a specially crafted ISO file containing malicious Rock Ridge extensions, it fails to properly validate pointer references before attempting memory operations. The function assumes certain data structures will be properly initialized, but malicious input causes these assumptions to fail, resulting in a null pointer dereference. This type of vulnerability falls under CWE-476 which specifically addresses NULL Pointer Dereference conditions in software implementations. The flaw occurs during the processing of ISO filesystem metadata where the library attempts to reallocate memory for symbolic link information without proper null checks.
From an operational perspective, this vulnerability presents a significant denial of service risk that can be exploited remotely without authentication. An attacker can craft a malicious ISO file and deliver it to a system running vulnerable software that processes ISO images, such as optical media burning applications, virtualization platforms, or media players. The impact extends beyond simple service disruption as this vulnerability can cause applications to crash or become unresponsive, potentially affecting critical systems that rely on ISO file processing. The remote exploitation capability means that attackers can trigger this vulnerability from any location, making it particularly dangerous in networked environments where ISO files might be processed automatically. This aligns with ATT&CK technique T1499.001 which covers network denial of service attacks through system resource exhaustion or application crashes.
The remediation strategy for CVE-2017-18199 requires immediate upgrading to GNU libcdio version 1.0.0 or later, where the null pointer dereference has been addressed through proper input validation and pointer checking mechanisms. System administrators should prioritize patching all affected systems, particularly those handling untrusted ISO files or serving as ISO processing endpoints. Additional mitigations include implementing proper input sanitization for ISO file processing, deploying network segmentation to limit exposure, and monitoring for unusual application crashes or service disruptions. Organizations should also consider implementing automated vulnerability scanning to identify systems running vulnerable versions of the library. The fix implemented in version 1.0.0 likely includes enhanced error handling and validation routines that prevent the null pointer dereference condition from occurring during Rock Ridge extension processing. Security teams should conduct thorough testing of patched systems to ensure that the vulnerability has been properly resolved without introducing regressions in functionality.