vLLM is an inference and serving engine for large language models. Prior to 0.24.0, the input_audio handling path for /v1/chat/completions calls AudioMediaIO.load_bytes or AudioMediaIO.load_file without passing VLLM_MAX_AUDIO_DECODE_DURATION_S to the shared audio decoder. An unauthenticated client can therefore submit a small compressed audio input that expands into a very large float32 PCM allocation, bypassing the duration guard already used by /v1/audio/transcriptions and causing an out-of-memory worker crash. Inline data URLs reach this path without being bounded by VLLM_AUDIO_FETCH_TIMEOUT. The issue affects deployments serving an audio-capable model, and authentication changes only the deployment-specific reachability. This issue is fixed in version 0.24.0.

Affected: PyPI: vllm

### Summary The audio decode-duration guard (`max_duration_s`, env `VLLM_MAX_AUDIO_DECODE_DURATION_S`, default 600s) that protects against audio decompression-bomb DoS is wired into **only** the speech-to-text path (`/v1/audio/transcriptions`). The **chat** audio path (`/v1/chat/completions`, `input_audio` content parts) calls the same decoder with **no** limit, so an **unauthenticated** client can submit a few-KB compressed audio file that expands to multiple GB of float32 PCM at decode time, OOM-killing the worker. This is a distinct sibling of **CVE-2026-5497** (video frame-count bomb, `VideoMediaIO.load_base64`) and **GHSA-pq5c-rjhq-qp7p** (image) in the same media subsystem.

Verified against `main` at HEAD `d78650c` (2026-06-16); applicable to the latest release v0.23.0.

### Details The guard rejects long audio *during* decode (before allocation), implemented in `vllm/multimodal/media/audio.py`: - `load_audio_pyav` — metadata reject (~82-98) and live sample-count reject (~129-136) - `load_audio_soundfile` — frames reject (~165-174)

All are gated on `if max_duration_s is not None`.

It is passed in exactly **one** place — the transcription serving layer: ```python # .../speech_to_text/base/serving.py:~170-174 load_audio(buf, sr=..., max_duration_s=self.max_audio_decode_duration_s) # self.max_audio_decode_duration_s = envs.VLLM_MAX_AUDIO_DECODE_DURATION_S (default 600) ```

The chat path never threads it: ```python # vllm/multimodal/media/audio.py:237-238 def load_b…