CVE-2021-45385 in ffjpeg
Summary
by MITRE • 02/11/2022
A Null Pointer Dereference vulnerability exits in ffjpeg d5cfd49 (2021-12-06) in bmp_load(). When the size information in metadata of the bmp is out of range, it returns without assign memory buffer to `pb->pdata` and did not exit the program. So the program crashes when it tries to access the pb->data, in jfif_encode() at jfif.c:763. This is due to the incomplete patch for CVE-2020-13438.
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Analysis
by VulDB Data Team • 02/17/2022
The vulnerability described in CVE-2021-45385 represents a critical null pointer dereference flaw within the ffjpeg library version d5cfd49, specifically affecting the bmp_load() function. This issue emerges when processing bitmap image files where the size metadata contains values that exceed acceptable ranges, creating a scenario where the program fails to properly initialize memory allocation for the data buffer. The root cause stems from an incomplete remediation of a previous vulnerability, CVE-2020-13438, which demonstrates how remediation efforts can sometimes introduce new failure points if not thoroughly validated. The vulnerability manifests when the program attempts to process bitmap files with malformed metadata, leading to a situation where the pb->pdata pointer remains uninitialized while the program continues execution.
The technical implementation of this flaw occurs within the bmp_load() function where size validation checks are insufficient to prevent malformed data from proceeding to subsequent processing stages. When size parameters in the bitmap metadata exceed expected boundaries, the function returns early without properly assigning memory to the pb->pdata buffer, leaving it as a null pointer. This incomplete error handling creates a dangerous state where the program continues execution flow without proper resource initialization. The subsequent crash occurs in the jfif_encode() function at line 763 of jfif.c, where the program attempts to access the uninitialized pb->data pointer, resulting in a segmentation fault or null pointer dereference exception. This pattern of error handling failure aligns with CWE-476, which specifically addresses null pointer dereference vulnerabilities in software systems.
The operational impact of this vulnerability extends beyond simple program crashes to potentially enable denial of service attacks against applications that utilize the ffjpeg library for image processing. Attackers can craft malicious bitmap files with oversized metadata fields to trigger the null pointer dereference, causing applications to terminate unexpectedly and potentially disrupting service availability. This vulnerability particularly affects systems that process untrusted image files, such as web applications, image processing servers, or content management systems that handle user-uploaded bitmap images. The incomplete patch for CVE-2020-13438 suggests that the development team may have focused on preventing one specific attack vector while inadvertently creating a new failure mode that can be exploited through different input conditions. This demonstrates the complexity of vulnerability remediation and the importance of comprehensive testing when addressing security issues.
Mitigation strategies for CVE-2021-45385 should prioritize immediate patching of the ffjpeg library to a version that properly handles all edge cases in bitmap metadata processing. Organizations should implement strict input validation for all image file processing pipelines, ensuring that size parameters are thoroughly validated before any memory allocation occurs. Additional defensive measures include implementing sandboxing mechanisms for image processing operations, using memory protection techniques such as stack canaries, and establishing robust error handling routines that prevent execution flow from continuing with uninitialized pointers. From an operational security perspective, regular security audits of third-party libraries and maintaining up-to-date vulnerability databases are essential for identifying and addressing similar issues before they can be exploited. The ATT&CK framework categorizes this type of vulnerability under software exploitation techniques, specifically targeting memory corruption vulnerabilities that can lead to system compromise or service disruption.