Y5neKO/CVE-2026-8461-EXP

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PoC files

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Analysisdeepseek-v4-pro:cloud ·

Technical assessment

The artifact is a full exploit generator for CVE-2026-8461, a heap out-of-bounds write in FFmpeg's MagicYUV decoder. It includes a Python script (exploit_cve_2026_8461.py) that crafts a malicious AVI file to overwrite an AVBuffer function pointer with the address of system(), achieving arbitrary command execution. The repository also contains calibration scripts and a detailed technical writeup.

Backdoor review

No backdoor observed in reviewed code

The repository contains a documented proof-of-concept exploit for CVE-2026-8461, a heap out-of-bounds write vulnerability in FFmpeg's MagicYUV decoder. The exploit chain uses the vulnerability to overwrite an AVBuffer function pointer with the address of system() and execute an attacker-supplied shell command. All behavior is consistent with the stated exploit goal against the vulnerable FFmpeg target. No concealed backdoor, unrelated payload, or operator-directed harm beyond the declared exploit was observed.

ClassificationExploit
Model confidence100%
AuthenticationNot required
LanguagesPythonMarkdown
Target softwareFFmpeglibavcodec
Attack typesHeap Out-of-Bounds WriteArbitrary Code Execution
Evidence & reasoningClassification basis · observed behavior · safety review
Technical evidence

Classification basis and observed behavior

Classification basis

The primary artifact is classified as an exploit because it contains functional code (exploit_cve_2026_8461.py) designed to generate a malicious input that exercises a vulnerability to achieve arbitrary code execution, not merely detect it. The script's docstring and README explicitly state it is a 'Full RCE Exploit Generator' that implements a chain from OOB Write to system() call.

exploit_cve_2026_8461.py:1-6README.md:1-5

Requirements

  • ASLR must be globally disabled (kernel.randomize_va_space=0) for the exploit's hardcoded addresses to be valid.README.md:47exploit_cve_2026_8461.py:19
  • A calibration step must be performed on the target machine to determine the exact heap layout, including the address of system() and the offset of the AVBuffer struct.README.md:62-81exploit_cve_2026_8461.py:25-28
  • The target must be running a vulnerable version of FFmpeg (≤ 8.0.1) on x86_64 with glibc malloc.CVE-2026-8461_Analysis.md:15-18exploit_cve_2026_8461.py:20

Observed behavior

  • The exploit_cve_2026_8461.py script generates a malicious AVI file. When this file is decoded by a vulnerable FFmpeg, it triggers a 640-byte heap out-of-bounds write.exploit_cve_2026_8461.py:1-6CVE-2026-8461_Analysis.md:3
  • The out-of-bounds write is used to overwrite the 'free' function pointer in an adjacent AVBuffer struct with the address of system(), and the 'opaque' field with a pointer to a shell command string also placed on the heap.exploit_cve_2026_8461.py:192-238CVE-2026-8461_Analysis.md:179-210
  • When the decoded frame is freed, the hijacked function pointer is called, resulting in the execution of the attacker-supplied shell command (e.g., 'id > /tmp/pwned').CVE-2026-8461_Analysis.md:505-512README.md:108-113
Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Exploit Chain
OOB write → AVBuffer.free hijack → system() callThe exploit generator (exploit_cve_2026_8461.py) builds a crafted AVI file that triggers a heap out-of-bounds write in FFmpeg's MagicYUV decoder, overwrites the AVBuffer.free function pointer with system(), and places a shell command on the heap. When the frame is freed, system(cmd) is called.exploit_cve_2026_8461.py:192-238CVE-2026-8461_Analysis.md:132-210
Command Execution
system("id > /tmp/pwned")The exploit is designed to execute an arbitrary shell command via system(). The README and analysis documents show the expected result: the command executes, then the process crashes due to heap corruption.README.md:88-113CVE-2026-8461_Analysis.md:485-512
Calibration Requirement
ASLR must be disabled (kernel.randomize_va_space=0) and heap layout must be calibrated for the target binary and AVI path.The exploit requires a calibration step to determine the exact heap addresses of system() and the command string, as well as glibc chunk metadata that must be preserved. This is documented as a prerequisite for the exploit to work.README.md:42-48CVE-2026-8461_Analysis.md:277-282
Review boundaries

What the analysis did not establish

  • The evidence includes two calibration scripts (auto_calibrate.py, auto_calibrate_nosym.py) and a binary file (ffmpeg_prod) that are not included in the selected text, limiting full analysis of the calibration process.
  • The exploit is explicitly limited to x86_64 architectures with ASLR disabled, as stated in the documentation.
  • The analysis is based solely on the provided text; the code was not executed, and its reliability or safety is not verified.
  • The evidence packet includes only 4 of 7 files in the repository. Two Python scripts (auto_calibrate.py, auto_calibrate_nosym.py) and one binary file (ffmpeg_prod) were omitted. The binary file was flagged as metadata-only and not analyzed. The omitted scripts are described in the README and analysis documents as calibration tools, but their source code was not reviewed.
  • The repository contains a non-text media file (images/image-20260624151409029.png) that was not analyzed.
Model interpretation

This review is limited to the supplied PoC code and context. It does not assert that the code works or is safe to execute.

Linked vulnerabilities

1