CVE-2026-119729 in GStreamer
Summary
by MITRE • 10/30/2026
A flaw was found in GStreamer. An integer overflow vulnerability in the AV1 LEB128 variable-length integer parser allows a remote attacker to cause a crash in applications that process AV1 media content. By crafting a malformed AV1 bitstream containing an invalid LEB128-encoded value, an attacker can cause integer overflow in the parser, resulting in incorrect length values being used during stream processing, which can lead to a denial of service.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified within GStreamer represents a critical security flaw located specifically in the AV1 media codec implementation, targeting the LEB128 variable-length integer parsing mechanism. This component is responsible for decoding multi-byte integers encoded using Little-Endian Base 128 format, which is standard in many modern multimedia containers and codecs including AV1. The core technical issue stems from an insufficient validation of input data during the parsing process. When a remote attacker crafts a maliciously constructed AV1 bitstream containing invalid or malformed LEB128-encoded values, the parser fails to correctly handle potential edge cases where the decoded integer exceeds the maximum value representable by the target variable type. This failure results in an integer overflow condition, where the calculated length or offset wraps around to a small positive number rather than triggering a proper error state or rejecting the input outright.
From a technical perspective, this flaw is classified under CWE-190: Integer Overflow or Wraparound. The consequence of this arithmetic error is severe because it directly influences memory allocation and buffer management operations downstream in the media processing pipeline. When the parser returns an incorrect length value due to the overflow, subsequent functions may allocate insufficient buffers or attempt to read beyond allocated memory boundaries. In many implementations, particularly those relying on strict bounds checking based on these parsed values, this discrepancy leads to out-of-bounds reads or writes. However, in the specific context described for GStreamer, the immediate and most prevalent outcome is a crash of the application processing the media content. This occurs because the invalid length value disrupts the internal state machine of the decoder, leading to segmentation faults or unhandled exceptions that terminate the process abruptly.
The operational impact of this vulnerability is primarily centered on Denial of Service (DoS). An attacker who can deliver a crafted AV1 file or stream to a victim using GStreamer-based applications such as web browsers, media players, or video conferencing software can trigger this crash remotely without requiring any user interaction beyond opening the malicious content. This poses a significant risk in environments where users are expected to view multimedia content from untrusted sources, including email attachments, social media platforms, and streaming services that utilize GStreamer for playback. The ability to cause an application crash effectively denies service to legitimate users and can be leveraged as part of larger attack chains to facilitate further exploitation if the initial crash allows for memory corruption or information disclosure in other contexts.
This vulnerability aligns with MITRE ATT&CK technique T1496: Resource Hijacking, specifically under the sub-technique of Denial of Service via resource exhaustion or application instability. While the primary effect is a crash rather than sustained resource consumption, the mechanism fits within the broader category of disrupting system availability through exploitation of software defects. Security professionals and developers must recognize that media parsers are frequent targets for such attacks due to their complexity and the necessity of processing untrusted external data streams. The lack of robust input validation in variable-length integer parsing routines is a common pattern in legacy codebases, making this type of vulnerability prevalent across various multimedia frameworks beyond just GStreamer.
To mitigate this risk, immediate patching of the affected GStreamer version is required to ensure that the AV1 LEB128 parser includes rigorous bounds checking and overflow detection logic. Developers should implement strict validation routines that verify whether a decoded integer exceeds expected limits before using it for memory operations or stream positioning. Additionally, adopting defensive programming practices such as using safe arithmetic libraries that detect overflows at compile time can prevent similar issues in future updates. For end-users, applying security patches promptly and utilizing sandboxed environments for viewing untrusted media content reduces the attack surface. Security teams should also monitor for new CVEs related to GStreamer’s codec implementations and ensure that intrusion detection systems are configured to flag anomalous traffic patterns associated with malformed multimedia streams attempting to exploit parser vulnerabilities.