CVE-2026-119842 in Red Hat
Summary
by MITRE • 10/30/2026
A flaw was found in GStreamer's gst-plugins-base MicroDVD subtitle parser. When processing a specially crafted subtitle file, the parser may dereference a NULL pointer, causing the application to crash when a user opens or plays media with a malformed MicroDVD (.sub) subtitle file.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified within the GStreamer multimedia framework specifically targets the gst-plugins-base component and its handling of MicroDVD subtitle files. This flaw manifests as an out-of-bounds read condition, technically classified under CWE-125 which denotes Out-of-Bounds Read. The root cause lies in the parsing logic for .sub files that adhere to the MicroDVD format specification. When a specially crafted or malformed subtitle file is processed by the application, the parser fails to adequately validate buffer boundaries before accessing memory locations associated with subtitle timing and text data. This lack of rigorous input validation allows the software to attempt reading from an invalid memory address, leading directly to a NULL pointer dereference event.
From a technical perspective, this defect represents a critical failure in boundary checking during the parsing phase of media processing pipelines. GStreamer is widely utilized across various Linux distributions and embedded systems for handling audio and video streams, often integrating subtitle rendering as part of the playback experience. When an application utilizing these plugins attempts to open or play media containing such a malformed MicroDVD file, the internal state machine encounters unexpected data structures that do not conform to expected lengths or offsets. Instead of gracefully rejecting the invalid input or triggering a controlled error handling routine, the parser proceeds with memory access operations based on corrupted indices. This results in the application attempting to dereference a NULL pointer, which is an operation prohibited by modern operating system security models and immediately triggers a segmentation fault.
The operational impact of this vulnerability is primarily centered around availability rather than confidentiality or integrity. The immediate consequence for end-users is that any media player relying on GStreamer will crash unexpectedly when encountering the malicious subtitle file. This denial of service effect disrupts normal workflow and can lead to data loss if unsaved work exists in the application at the time of the crash. While the primary vector described involves local execution through opening a file, this type of vulnerability is often exploitable for remote code execution or privilege escalation if combined with other vulnerabilities within the same attack chain, although the current description highlights only the crash scenario. Attackers could distribute maliciously crafted subtitle files via email attachments, compromised websites, or shared network drives to trigger this behavior in unsuspecting users who open media content without realizing the embedded threat.
Mitigation strategies for this vulnerability involve both immediate patching and long-term defensive coding practices. The most effective remediation is to apply the specific software update provided by the GStreamer maintainers that addresses the boundary check logic within the MicroDVD parser. System administrators should ensure that all systems running affected versions of gst-plugins-base are updated to a version where this NULL pointer dereference has been resolved through proper input sanitization and bounds checking. Additionally, organizations can implement network-level filtering or application whitelisting to restrict the execution of untrusted media files until patches are deployed. From a development standpoint, integrating static analysis tools that detect out-of-bounds reads and enforcing strict adherence to CWE-20 Improper Input Validation guidelines during code review processes will help prevent similar defects in future releases. Security teams should also monitor for related advisories as attackers may attempt to chain this denial of service flaw with other vulnerabilities to achieve more severe outcomes such as arbitrary code execution within the context of the media player process.