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HIGH severity

Phantom: Arbitrary file write and decode-bomb DoS via unconfined MCP tool pathsGHSA-52vm-mxx8-f227

HIGH

GHSA-52vm-mxx8-f227 is a high-severity (CVSS 7.7) remote code execution vulnerability in phantom-audio. A fix is available for phantom-audio — see the affected versions and patch details below.

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Jul 9, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected
🐍phantom-audio

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

In Phantom <= 1.3.0, when PHANTOM_OUTPUT_DIR was unset (the default), the MCP tools accepted arbitrary absolute output paths with no confinement. Anything able to send tool calls (e.g. an AI agent driving the MCP interface) could write or overwrite arbitrary files the process user can write — including shell startup files (~/.zshrc) or a Reaper __startup.lua, which is effectively local code execution on a developer workstation.

Separately, the stem-separation and render paths decoded input audio with no size/duration cap (the analysis path was already guarded). A small, highly compressed FLAC/OGG could expand to multi-gigabyte PCM, causing memory-exhaustion DoS, and widened exposure to decoder bugs including libsndfile CVE-2026-37555.

Patches

Fixed in 1.3.1:

  • File writes are always confined to PHANTOM_OUTPUT_DIR (default ~/.phantom/output); symlinks resolved and re-verified on the final path.
  • Decode/duration/size guards mirrored onto the separation and render paths (plus ffmpeg -max_alloc/-t/-fs).
  • Atomic O_CREAT|O_EXCL output creation in reference matching and symlink-TOCTOU hardening on confined input reads.

Workarounds

Set PHANTOM_OUTPUT_DIR (and optionally PHANTOM_AUDIO_DIR) to dedicated directories before starting the server.

Credit

Found during an internal security audit.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIphantom-audioall versions1.3.1pip install --upgrade 'phantom-audio==1.3.1'

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phantom-audio, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update phantom-audio to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-52vm-mxx8-f227 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### Impact In Phantom <= 1.3.0, when `PHANTOM_OUTPUT_DIR` was unset (the default), the MCP tools accepted arbitrary absolute output paths with no confinement. Anything able to send tool calls (e.g. an AI agent driving the MCP interface) could **write or overwrite arbitrary files** the process user can write — including shell startup files (`~/.zshrc`) or a Reaper `__startup.lua`, which is effectively local code execution on a developer workstation. Separately, the stem-separation and render paths decoded input audio with no size/duration cap (the analysis path was already guarded). A small,
O3 Security · Impact-Aware SCA

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