CVE-2023-41064, CVE-2023-4863, CVE-2023-5129: Frequently Asked Questions for ImageIO and WebP/libwebp Zero-Day Vulnerabilities

Frequently asked questions relating to vulnerabilities in Apple, Google and the open source libwebp library.

Background

The Tenable Security Response Team has put together this blog to answer frequently asked questions (FAQ) to help provide clarity around recently disclosed vulnerabilities including CVE-2023-41064, CVE-2023-4863 and CVE-2023-5129 in an open source library called libwebp.

FAQ

What do these vulnerabilities have to do with Apple products?

On September 7, researchers at Citizen Lab published a blog post detailing their discovery of an iPhone zero-click, zero-day exploit chain in Apple iOS used to deploy a spyware known as Pegasus.

NEW: Last week, we @citizenlab captured a “zero-click” exploit used to install Pegasus on the latest version of iOS, 16.6. The exploit installed Pegasus without any interaction from the victim, and was virtually invisible https://t.co/MxPrAThwa1

— Bill Marczak (@billmarczak) September 7, 2023

What are the vulnerabilities that Apple patched?

Apple patched two vulnerabilities across several of its operating systems, including iOS and iPadOS [1, 2], watchOS and several versions of macOS [1, 2, 3]:

What is this exploit chain called and how severe is it?

The Citizen Lab dubbed this exploit chain BLASTPASS and it is considered a critical flaw because exploitation requires no interaction from a potential victim, making it a zero-click vulnerability.

In-the-wild exploitation involved attachments using Apple PassKit that contained malicious images delivered to the victim via iMessage.

What does this have to do with Google Chrome and other web browsers?

As part of the disclosure of these vulnerabilities, both Apple’s Security Engineering and Architecture (SEAR) team and The Citizen Lab notified Google about their findings on September 6 due to the potential for exploitation outside of Apple’s ecosystem.

Did Google also patch this vulnerability?

Yes, on September 11, Google published a patch for Google Chrome. However, they assigned a separate CVE for this vulnerability:

What is ImageIO or Image I/O?

ImageIO or Image I/O is a framework that allows programs to read and write image file formats, including WebP. It is a part of Apple operating systems from iOS and iPadOS to macOS, and watchOS.

What is WebP or libwebp?

WebP is an open-source image file format developed by Google, while libwebp is a library that was developed to allow programs to support the WebP file format. It is part of Google’s Chromium project, the open source web browser that Google Chrome and other browsers are based on.

How are CVE-2023-4863 and CVE-2023-41064 connected?

Based on the timeline of when CVE-2023-41064 was disclosed (September 7) and both Apple and The Citizen Lab’s proactive disclosure to Google on September 6, coupled with the fact that both issues are buffer overflow vulnerabilities in image processing frameworks/libraries (ImageIO, WebP), it would appear that both vulnerabilities are related. This is also corroborated by other independent research from Matt Suiche and Ben Hawkes.

We suspect that this is the same bug that Citizen Lab reported to Apple after detecting an NSO Group exploit chain called “BLASTPASS” that was used to attack on a Washington DC-based civil society organization.

— Ben Hawkes (@benhawkes) September 21, 2023

If this affects the libwebp library, does that mean other programs are also vulnerable?

Yes, applications or programs and operating systems that use libwebp as a dependency are also considered vulnerable to these flaws.

What does CVE-2023-5129 have to do with this?

On September 25, Google assigned a new CVE, CVE-2023-5129, to expand the impact of CVE-2023-4863, to cover libwebp more broadly versus specifically impacting Google Chrome.

Google also assigned a maximum CVSSv3 score of 10.0 for this CVE.

Did Google reject CVE-2023-5129 after assigning it?

Yes, on September 27, Google rejected CVE-2023-5129, citing it as a duplicate of CVE-2023-4863 and updated the description for CVE-2023-4863 to include the impact to libwebp itself while clarifying the critical impact to Chromium.

Google did not increase the CVSSv3 score for CVE-2023-4863, opting instead to add a note about it being of “Critical” per Chromium security’s severity scale.

Why was CVE-2023-5129 rejected?

Google has not confirmed why it rejected the vulnerability. However, based on the fact that several vendors have already adopted CVE-2023-4863 as the CVE identifier when patching libwebp, it likely did not make sense to assign a new CVE for this versus expanding the impact of the original CVE.

How many applications or programs are affected by CVE-2023-4863?

Because libwebp is a library that is included in applications and programs or packages as a dependency, we do not know the full depth and breadth of how widespread it is. We know that several browsers, including Firefox and Thunderbirdas well as browsers based on Chromium including Microsoft Edge, Opera and Brave are affected by this vulnerability. Additionally, the library is included in the Electron open source framework that is used by a large number of applications including 1Password, Slack and more.

A list of affected Electron applications is being tracked by Michael Taggart here.

Timeline

The following is a timeline related to all three vulnerabilities highlighted in this FAQ. It was last updated on September 27.

Identifying affected systems

A list of Tenable plugins to identify affected systems can be located on the individual CVE page for each of the CVEs mentioned here:

These links will display all available plugins for these vulnerabilities, including upcoming plugins in our Plugins Pipeline.

Get more information

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