CVE-2026-100756 in Firefox
Summary
by MITRE • 09/29/2026
Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
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Analysis
by VulDB Data Team • 09/29/2026
The identified security issue resides within the Audio/Video playback subsystem of Mozilla Firefox, specifically involving incorrect boundary conditions that can lead to memory safety violations. This type of vulnerability typically arises when the software fails to properly validate input data or internal state variables before performing operations on allocated memory buffers. In the context of media playback engines, such errors often manifest as out-of-bounds reads or writes, which occur when an index or pointer exceeds the limits of a designated buffer region. These flaws are particularly dangerous because they can be triggered by maliciously crafted multimedia content embedded in web pages, allowing attackers to exploit the browser's processing logic without requiring user interaction beyond visiting the compromised site.
From a technical perspective, boundary condition errors fall under the Common Weakness Enumeration category CWE-125 for out-of-bounds read or CWE-787 for out-of-bounds write, depending on whether the vulnerability allows unauthorized data access or memory corruption. When an attacker crafts media files with specific header anomalies or malformed stream structures, they can manipulate internal pointers to point outside valid memory regions. If the browser does not adequately check these boundaries before accessing memory, it may read sensitive information from adjacent memory locations, leading to a potential information disclosure vulnerability. Conversely, if the operation involves writing data, it could overwrite critical program state or return addresses, potentially facilitating arbitrary code execution with the privileges of the user running the browser process.
The operational impact of this vulnerability is significant due to its presence in widely used web browsers that handle untrusted content from the internet daily. Successful exploitation could allow a remote attacker to execute arbitrary code on the victim's system by leveraging memory corruption techniques such as heap spraying or control flow hijacking. This aligns with several tactics and techniques within the MITRE ATT&CK framework, particularly those related to initial access via browser exploits and subsequent execution phases where malicious payloads are deployed through compromised plugins or renderer processes. The risk is amplified because modern browsers employ complex multi-process architectures, but a successful exploit in one process can sometimes lead to sandbox escape if additional vulnerabilities exist or if the boundary condition affects shared memory structures between processes.
To mitigate this risk, users must ensure that their Firefox installations are updated to include the fixes provided in versions 153.4 and 157 for standard releases, as well as ESR versions 115.42 and 140.17 for extended support channel deployments. These updates contain patches that enforce stricter validation of buffer boundaries during media decoding operations, ensuring that any access to memory is verified against allocated limits before execution proceeds. Organizations relying on Firefox should prioritize patching their endpoints immediately upon applying these version upgrades. Additionally, implementing browser hardening techniques such as disabling unnecessary plugins and using content security policies can reduce the attack surface presented by malicious web content. Regular monitoring of vendor advisories remains essential for maintaining defense-in-depth against evolving media-based exploitation vectors that target boundary condition flaws in rendering engines.