CVE-2026-119727 in Red Hat
Summary
by MITRE • 10/30/2026
A flaw was found in GStreamer's gst-plugins-bad H.265 video parser. When parsing a specially crafted H.265 bitstream containing a Screen Content Coding (SCC) extension with certain palette predictor initializer settings, an integer underflow in the upper-bound computation allows the parser to accept an out-of-range value for the number of palette predictor entries. This causes the parser to write beyond the end of a fixed-size array, resulting in memory corruption and an application crash. Successful exploitation requires an attacker to provide a malformed H.265 media file to a vulnerable application, and is limited to a denial-of-service impact.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified within GStreamer's gst-plugins-bad component specifically targets the H.265 video parser when processing streams that utilize the Screen Content Coding extension. This technical flaw manifests as an integer underflow during the computation of upper-bound values for palette predictor entries. In standard H.265 decoding, particularly with SCC extensions used frequently in screen sharing and remote desktop scenarios, precise boundary checks are critical to ensure memory safety. The parser fails to correctly validate the number of palette predictor initializer settings provided in a specially crafted bitstream. Because the arithmetic operation results in an underflowed value, the resulting integer is interpreted as a large positive number rather than a negative or invalid state. This erroneous calculation allows the application to accept out-of-range values for array indexing operations that govern memory allocation and access patterns within the decoder's internal structures.
The operational consequence of this logic error is a heap-based buffer overflow where the parser writes data beyond the allocated boundaries of a fixed-size array. Memory corruption occurs immediately upon processing the malformed segment, leading inevitably to application instability or crash. The primary impact of this vulnerability is a denial-of-service condition against applications that rely on GStreamer for H.265 video playback or streaming. While memory corruption vulnerabilities often carry risks of arbitrary code execution, in this specific instance, the exploitation vector is constrained by the nature of the input and the affected component's typical usage patterns. Successful exploitation requires an attacker to supply a maliciously crafted H.265 media file to a vulnerable application that utilizes GStreamer for decoding. The attack does not appear to provide direct control over instruction pointers or arbitrary memory writes sufficient for code execution, thereby limiting the impact primarily to service disruption and resource exhaustion through repeated crashes.
From a classification perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound, which describes situations where an arithmetic operation exceeds the maximum value of the data type, leading to unexpected behavior such as underflow in signed integers that are subsequently used for unsigned array indexing. Furthermore, the attack vector corresponds to ATT&CK technique T1496 Resource Hijacking, specifically through denial-of-service mechanisms, and potentially T1059 Command and Scripting Interpreter if considered within a broader context of application exploitation chains, though here it remains isolated to availability impact. The vulnerability highlights the critical importance of rigorous input validation in multimedia parsers, where complex codec specifications like H.265 SCC introduce numerous edge cases that must be strictly bounded against memory limits.
Mitigation strategies should focus on immediate patching of the GStreamer gst-plugins-bad package to versions that include fixes for this integer underflow condition. Developers integrating GStreamer into their applications should ensure they are using updated library versions and consider implementing additional sandboxing or privilege separation mechanisms to limit the blast radius if a crash occurs. For end-users, avoiding playback of untrusted H.265 media files is recommended until patches are applied. Security teams monitoring for exploitation attempts should look for abnormal termination events in applications handling video streams, particularly those involving screen content coding extensions, as these may indicate attempted probing or successful denial-of-service attacks against the multimedia pipeline infrastructure.