0xBlackash/CVE-2026-8461

GitHubRepository PoCExploit

PoC files

2 files

File viewing is interactive and short-lived. Downloads are password-protected ZIP archives using password eip.

GitHub
Analysisdeepseek-v4-pro:cloud ·

Technical assessment

A Python script that generates a malicious AVI file containing a crafted MagicYUV frame designed to trigger an out-of-bounds write (CVE-2026-8461) in FFmpeg's libavcodec, overwriting an AVBuffer's free function pointer with system() to achieve remote code execution.

Backdoor review

No backdoor observed in reviewed code

The PoC is a Python script that generates a malicious AVI file to exploit CVE-2026-8461, an out-of-bounds write in FFmpeg's MagicYUV decoder. The script builds a crafted video frame with a payload designed to overwrite heap metadata and redirect execution to system() with a user-supplied command. All behavior is consistent with the disclosed exploit: the operator provides the command and target addresses, and the script produces an AVI file. No concealed, unrelated, or deceptive actions were found.

ClassificationExploit
Model confidence95%
AuthenticationNot required
LanguagesPython
Target softwareFFmpeglibavcodecMagicYUV decoder
Attack typesOut-of-bounds writeRemote code execution
Evidence & reasoningClassification basis · observed behavior · safety review
Technical evidence

Classification basis and observed behavior

Classification basis

The Python script is explicitly designed to generate a malicious media file that exploits CVE-2026-8461 to achieve remote code execution by corrupting heap metadata and hijacking a function pointer. It does not merely detect or report the vulnerability; it constructs and outputs an exploit payload.

CVE-2026-8461.py:3CVE-2026-8461.py:60-78CVE-2026-8461.py:150-153

Requirements

  • Target must be running a vulnerable version of FFmpeg (before 8.1.2) with the MagicYUV decoder.README.md:26-28
  • Attacker must know or calibrate target-specific memory addresses (system() and command heap address).CVE-2026-8461.py:40-44
  • Victim must process the generated AVI file with FFmpeg (e.g., ffmpeg -i exploit.avi -f null -).CVE-2026-8461.py:152-153

Observed behavior

  • Constructs a MagicYUV frame with an odd slice_height (31) to trigger an out-of-bounds write.CVE-2026-8461.py:18
  • Builds an out-of-bounds payload that overwrites an AVBuffer structure: sets refcount to 1, replaces the free function pointer with system(), and sets the opaque pointer to a heap address containing the attacker's command.CVE-2026-8461.py:60-78
  • Wraps the exploit frame in a minimal AVI container and writes it to a file.CVE-2026-8461.py:111-129
  • Accepts a shell command and calibration data (system address, command heap address) as command-line arguments.CVE-2026-8461.py:135-138
Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Command Execution
system()The payload overwrites an AVBuffer free function pointer with the address of system() and sets the opaque pointer to a heap address containing the user-supplied command. This is the disclosed RCE mechanism.CVE-2026-8461.py:75-76
User Supplied Input
--cmdThe operator must supply the command to execute via the --cmd argument. The script does not embed or hardcode any command.CVE-2026-8461.py:135
Target Addresses
system_addr, cmd_heap_addrThe operator must supply target-specific addresses (system() and command heap location) either via a calibration JSON file or command-line arguments. Default example addresses are provided but are clearly marked as examples.CVE-2026-8461.py:40-41CVE-2026-8461.py:137-138
Review boundaries

What the analysis did not establish

  • The AVI container construction is incomplete (line 122 notes 'more AVI headers omitted for brevity'), so the generated file may not be a fully valid AVI.
  • The exploit requires target-specific memory addresses (system() and command heap) that are not provided; default values are placeholders and unlikely to work without calibration.
  • The evidence does not include any demonstration or verification that the generated file successfully triggers the vulnerability or achieves code execution.
  • The AVI container creation function (create_avi) contains a comment indicating that some AVI headers are omitted for brevity (line 122). The generated AVI file may be incomplete or non-functional, but this does not introduce backdoor behavior.
  • The review is limited to the supplied text files; no binary files were present.
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