CVE-2023-37836 in libjpeg
Summary
by MITRE • 07/14/2023
libjpeg commit db33a6e was discovered to contain a reachable assertion via BitMapHook::BitMapHook at bitmaphook.cpp. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted file.
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Analysis
by VulDB Data Team • 01/18/2026
The vulnerability identified as CVE-2023-37836 resides within the libjpeg library, specifically in the BitMapHook::BitMapHook function located in bitmaphook.cpp. This issue represents a critical flaw that manifests through a reachable assertion, indicating that an attacker can trigger a deliberate program termination through carefully crafted input files. The vulnerability stems from insufficient input validation within the bitmap handling mechanism of the jpeg library, which is widely used for image processing across numerous applications and systems. The affected code path suggests that when the library processes malformed jpeg files containing specific bit patterns, it encounters an assertion failure that results in program termination rather than graceful error handling. This behavior creates a predictable denial of service condition that can be exploited by adversaries who understand the specific file format structures that trigger the assertion.
The technical implementation of this vulnerability involves the manipulation of jpeg file structures to force the BitMapHook::BitMapHook constructor to encounter an unexpected condition that triggers the assertion. This typically occurs when processing compressed image data that contains malformed headers or unexpected bit sequences that the library's bitmap handling code does not anticipate. The assertion failure represents a fundamental breakdown in the library's error handling capabilities, where instead of returning appropriate error codes or gracefully failing, the program terminates abruptly. This type of vulnerability falls under the CWE-617 category of reachable assertions, which specifically addresses conditions where assertions can be triggered by external input, leading to program termination and denial of service. The vulnerability demonstrates poor defensive programming practices where the library fails to distinguish between legitimate program errors and maliciously crafted input that should be handled gracefully.
From an operational impact perspective, this vulnerability presents a significant risk to systems that rely on libjpeg for image processing, including web applications, image servers, content management systems, and any software that accepts user-uploaded jpeg files. The denial of service condition can be exploited to crash applications or services that process jpeg images, potentially leading to complete service unavailability for legitimate users. Attackers can craft malicious jpeg files that, when processed by vulnerable applications, will trigger the assertion and cause the target system to terminate unexpectedly. This vulnerability is particularly dangerous in server environments where multiple concurrent image processing operations might be occurring, as a single malicious file could potentially take down an entire service. The impact extends beyond simple service disruption to include potential resource exhaustion if the exploitation involves repeated triggering of the assertion.
The exploitation of this vulnerability requires minimal technical expertise, as it only requires creating a specific type of jpeg file that triggers the assertion condition in the BitMapHook::BitMapHook function. This makes it particularly dangerous as it can be easily automated and used in mass exploitation campaigns. The vulnerability also demonstrates a lack of proper input sanitization and validation, which are fundamental security practices recommended by the OWASP Top Ten and other security frameworks. Organizations using libjpeg should consider implementing additional input validation layers, such as file format verification and size limitations, to mitigate the risk of exploitation. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, as it specifically targets the availability aspect of system security by causing service interruption through crafted input. Mitigation strategies should include immediate patching of the libjpeg library to the version that contains the fix for this assertion failure, along with implementing proper input validation and file type checking mechanisms at application level to prevent potentially malicious files from reaching the vulnerable library code.