Google Chrome use-after-free Vulnerability Leads to Remote Attack

Google Chrome has been recently discovered to be a Use-after-free vulnerability that threat actors can exploit to attack users. This vulnerability exists in the Google Chrome VideoEncoder, which can be triggered using a malicious web page.

However, Google Chrome version 113.0.5672.127 (64-bit) and Chromium 115.0.5779.0 (Build) (64-bit) were found to be vulnerable to this bug, which was fixed by Chrome developers in versions 114.0.5735.198 for Mac and Linux and 114.0.5735.198/199 for Windows.

CVE-2023-3421 – Google Chrome use-after-free

Use-after-free is a condition in which the memory allocation is freed, but the program does not clear the pointer to that memory. This is due to incorrect usage of dynamic memory allocation during an operation. 

CVE-2023-3421 vulnerability arises due to this use-after-free condition in the VideoEncoder av1_svc_check_reset_layer_rc_flag functionality, which a threat actor can exploit by serving a malicious HTML page which can lead to heap corruption.

The severity for this vulnerability has been given as 8.8 (High).  Furthermore, a proof-of-concept has been released for this vulnerability, which explains the vulnerability and possible exploitation. 

As per the reports, the media::Av1VideoEncoder::ChangeOptions function can be called multiple times by continuously switching the encoder configuration using a Javascript code.

This function executes the SetUpAomConfig function that prepares the configuration for the video encoder. This function is also used to configure the encoder without the scalability mode option set, leading to the SetUpAomConfig function not properly validating the svc_params.number_temporal_layers parameter.

In addition, svc->number_temporal_layers is forced to be set to “zero,” which will give the negative index used to get the svc->layer_context pointer. A complete report has been published by TALOS, providing detailed information about this vulnerability, exploitation, source code, and other information.

Users of Google Chrome 113.0.5672.127 (64-bit) and Google Chrome Chromium 115.0.5779.0 (Build) (64-bit) versions are recommended to upgrade to the latest versions to prevent this vulnerability from getting exploited.

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