In a critical turn of events that has left the tech world buzzing, a significant vulnerability designated as CVE-2023-4863 has been discovered in the WebP Codec. This bug is not confined to a single web browser but threatens multiple applications that utilize the libwebp library. The exploit is already being actively used in the wild, making immediate action imperative.

“Protecting against such vulnerabilities is crucial,” says Alex Ivanovs, who broke the news on September 13, 2023. So far, major browser vendors such as Google Chrome, Mozilla Firefox, Brave, and Microsoft Edge have confirmed fixes. But the risk isn’t over yet.

The Dreaded Heap Buffer Overflow: What Is It?

Imagine a shelf designed to hold only five books. If you try to jam a sixth one in, something’s got to give—either the shelf breaks, or another book gets pushed off. This is the essence of a “heap buffer overflow,” a type of computer vulnerability where too much data is stuffed into a designated area of memory, leading to all sorts of malicious possibilities.

“If someone knows a program has a heap buffer overflow vulnerability, they might be able to send it specially crafted data that causes the program to behave in unexpected ways,” warns Ivanovs. In layman’s terms, it’s an open invitation for hackers to run malicious code or gain unauthorized system access.

The WebP Quandary: More than Just a Browser Issue

This vulnerability affects not only browsers but any software that relies on the libwebp library. This encompasses a wide range of applications from Electron-based apps like Signal to other software like Honeyview and many Android and cross-platform apps built with Flutter.

The vulnerability is particularly alarming because it contradicts initial reports that suggested the issue was exclusive to Chrome. “CVE-2023-4863 was falsely marked as Chrome-only by Mitre and other organizations that track CVE’s and 100% of media reported this issue as ‘Chrome only,’ when it’s not,” Ivanovs clarifies.

Anatomy of the Flaw: Where Things Went Wrong

The vulnerability stems from the “BuildHuffmanTable” function in the WebP library. The problem occurs when more memory is allocated than should be, leading to the dreaded heap buffer overflow. While the fix involves tweaking this function, the situation underlines the limitations of even memory-safe languages in preventing such vulnerabilities.

A Historical Perspective: Learning from the GIF Format

This isn’t the first time image formats have been at the center of security concerns. The GIF format has had its share of vulnerabilities, exploited for everything from causing buffer overflows to triggering memory corruption. These past instances serve as cautionary tales underscoring the importance of software updates.

Vendor Actions: Timely Updates

Google has already released updates for Chrome, and Mozilla plans to roll out its Firefox update today. Even Apple seems to be in the mix, suggesting an impending update to tackle this vulnerability. “Users are urged to ensure their browsers are up-to-date with the latest versions to benefit from these crucial security patches,” says Ivanovs.

WebP: A Brief Overview

WebP is a modern image format developed by Google that offers superior lossless and lossy compression. Its widespread adoption makes the quick resolution of this issue all the more urgent.


The flaw was responsibly disclosed by the Apple Security Engineering and Architecture (SEAR) team in collaboration with The Citizen Lab at The University of Toronto’s Munk School on September 6, 2023. Google has also confirmed that an exploit for CVE-2023-4863 exists in the wild, heightening the urgency for immediate action.

Take Action Now

Your browser will restore your tabs upon restarting, so you have no excuse not to act immediately. Delaying updates exposes you to unnecessary risks. Secure your digital world by updating now.