Buffer Overflow in bitbank2 AnimatedGIF

Executive Summary

CVE-2026-30141 is a critical buffer overflow vulnerability found in the AnimatedGIF library, specifically in the DecodeLZW function responsible for decompressing GIF images.

The flaw occurs due to insufficient bounds checking during LZW decompression, which leads to heap-based buffer overflows when processing malformed LZW codes that exceed the expected maximum size.

Additionally, improper validation of certain internal indices further worsens heap corruption.

Attackers can exploit this vulnerability by crafting malicious GIF files that trigger the overflow, causing the application to crash or potentially allowing arbitrary code execution.

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Impact Analysis

This vulnerability can impact you by allowing remote attackers to cause denial-of-service (DoS) conditions, crashing applications that use the vulnerable AnimatedGIF library when processing malicious GIF files.

More severely, it may allow attackers to execute arbitrary code on the affected system, potentially leading to full system compromise depending on the context in which the library is used.

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Detection Guidance

This vulnerability can be detected by analyzing the behavior of the AnimatedGIF library when processing GIF files, especially by using fuzz testing or AddressSanitizer (ASan) to identify heap-buffer-overflow errors during LZW decompression.

A practical approach is to test the system or application with specially crafted GIF files that trigger the buffer overflow, observing for crashes such as SIGSEGV or SIGBUS signals.

While no specific commands are provided, using tools like AddressSanitizer with the application or running fuzz testing frameworks against the GIF decoding functionality can help detect the vulnerability.

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Mitigation Strategies

Immediate mitigation steps include implementing strict bounds checking in the DecodeLZW function to ensure that LZW codes do not exceed the expected maximum (typically 4096 for 12-bit LZW).

Additionally, validate GIF file dimensions and compressed data sizes before processing to prevent buffer overflows.

Input sanitization should be added to reject malformed or malicious GIF files that could trigger the vulnerability.

Until a patched version of the library is available, avoid processing untrusted or suspicious GIF files with the affected AnimatedGIF library.

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