CVE-2021-39583 in swftools
Summary
by MITRE • 09/20/2021
An issue was discovered in swftools through 20200710. A NULL pointer dereference exists in the function pool_lookup_string2() located in pool.c. It allows an attacker to cause Denial of Service.
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Analysis
by VulDB Data Team • 09/30/2021
The vulnerability identified as CVE-2021-39583 represents a critical null pointer dereference flaw within the swftools software suite, specifically affecting versions through 20200710. This issue manifests within the pool_lookup_string2() function located in the pool.c source file, creating a condition where the application fails to properly validate pointer references before attempting to access memory locations. The flaw stems from inadequate input sanitization and error handling mechanisms that permit maliciously crafted data to trigger unexpected program behavior.
The technical implementation of this vulnerability involves a scenario where the pool_lookup_string2() function receives input that leads to a null pointer being dereferenced during string lookup operations. This occurs when the function attempts to access memory through a pointer that has not been properly initialized or validated, resulting in an immediate program termination. The flaw is classified as a CWE-476 Null Pointer Dereference under the Common Weakness Enumeration framework, which specifically addresses the dangerous practice of dereferencing null pointers without proper validation. The vulnerability's exploitation path demonstrates a classic denial of service vector where an attacker can craft specific input sequences that force the application into an unrecoverable state.
From an operational impact perspective, this vulnerability creates a significant risk for systems relying on swftools for processing flash content or related multimedia files. The denial of service condition effectively renders the affected application unavailable to legitimate users, potentially disrupting critical business operations or content delivery services. Attackers can exploit this weakness by providing malformed input data that triggers the null pointer dereference, causing the application to crash and requiring manual intervention for recovery. The vulnerability's impact extends beyond simple service disruption as it can be leveraged in larger attack campaigns where multiple instances of the software are targeted to create cascading availability issues.
Security practitioners should implement immediate mitigations including updating to patched versions of swftools where available, implementing input validation controls at the application level, and deploying monitoring solutions to detect potential exploitation attempts. The ATT&CK framework categorizes this vulnerability under the T1499 technique for Network Denial of Service, highlighting the strategic importance of addressing such weaknesses in software components. Organizations should also consider implementing sandboxing mechanisms for processing untrusted flash content and establishing robust incident response procedures to handle potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper pointer validation and error handling in software development practices, particularly in applications handling external data inputs.