Is CVE-2026-109311 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-109311 being exploited in the wild.

How severe is CVE-2026-109311?

Medium severity, with a CVSS score of 6.5, published 12 October 2026.

Is there a fix for CVE-2026-109311?

Yes: fixed in vLLM 0.29.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-109311 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-109311?

Check whether you run Vllm at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-109311: vLLM heap overflow in audio transcription IAMF parser

CVE-2026-109311 · Severity: medium · CVSS 6.5 · Published 2026-10-12

vLLM is a large language model inference engine that includes audio transcription capabilities. An authenticated attacker can upload a malicious IAMF audio file to the transcription endpoint that exploits a heap overflow vulnerability in FFmpeg's audio parser, causing the API process to crash and denying service to all users of that server.

Technologies: Vllm. Vendors: Vllm.

Quick answers

Is CVE-2026-109311 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-109311 being exploited in the wild.
How severe is CVE-2026-109311?: Medium severity, with a CVSS score of 6.5, published 12 October 2026.
Which products and versions are affected?: Vllm before 0.29.0.
Is there a fix for CVE-2026-109311?: Yes: fixed in vLLM 0.29.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-109311 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-109311?: Check whether you run Vllm at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: vLLM 0.29.0

Technical details

vLLM's /v1/audio/transcriptions endpoint fails to properly validate uploaded audio before passing it to FFmpeg via PyAV's av.open(). When soundfile cannot parse the container format, the raw untrusted audio bytes reach FFmpeg's IAMF parser with only a file-size check applied. A crafted IAMF container triggers a heap buffer overflow in FFmpeg's scalable_channel_layout_config() function, corrupting heap memory and crashing the process. Authentication is required to reach the endpoint, but exploitation is straightforward via repeated uploads of malformed IAMF containers.

Affected products

vLLM vLLM before 0.29.0

Timeline

2026-09-28: disclosed
2026-10-12: advisory

References

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