CVE-2026-3084: Critical Integer Underflow in GStreamer H.266 Codec Parser Enables Remote Code Execution

A critical vulnerability in the GStreamer multimedia framework, identified as CVE-2026-3084, allows remote attackers to execute arbitrary code on affected systems. The flaw, reported by the Zero Day Initiative as ZDI-26-169, stems from an integer underflow within the H.266 codec parser, specifically during the parsing of picture partitions. GStreamer has released a patch to address the issue.

The flaw resides in the lack of proper validation of user-supplied data, which can result in an integer underflow before writing to memory. This memory corruption can be leveraged by an attacker to execute arbitrary code in the context of the current process. The vulnerability carries a CVSS score of 7.8, classified as high severity, with the attack vector being local but requiring user interaction.

To exploit this vulnerability, an attacker must trick a user into processing a malicious file, such as a crafted video file. The attack vectors may vary depending on the implementation, but the core requirement is that the victim interacts with the malicious content through an application that relies on the GStreamer library. This makes the vulnerability particularly concerning for applications that automatically process multimedia files, such as media players, web browsers, and video conferencing tools.

GStreamer is a widely used open-source multimedia framework that serves as the backbone for many Linux-based media applications, including GNOME's Totem video player, the Rhythmbox music player, and various video editing software. It is also integrated into embedded systems and IoT devices. The widespread adoption of GStreamer means that the potential impact of this vulnerability is significant, affecting a broad range of systems and applications.

The vulnerability was reported to GStreamer on February 11, 2026, and the coordinated public release of the advisory occurred on March 6, 2026. GStreamer has issued an update to correct the vulnerability, which can be found in the commit 496e4f296e658fba7fd40027d3bbe6095633ec91 on the GStreamer GitLab repository. Users and administrators are strongly advised to update their GStreamer installations to the latest patched version as soon as possible.

This vulnerability highlights the ongoing challenges in securing complex multimedia processing libraries, which often handle a wide variety of codecs and file formats and codecs. Integer underflow and overflow bugs are common in such libraries due to the intricate parsing logic required. The disclosure of this flaw serves as a reminder for developers to rigorously validate user-supplied data and for users to keep their software up to date to mitigate the risk of exploitation.