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Low, CVSS 3.1amended

vLLM: Harmony tool continuations drop cache_salt — restoring a cross-tenant prefix-cache membership oracle

CVE-2026-105752GHSA-935w-9g4m-p28p

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (vllm 0.30.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI vllm

    Affected
    < 0.30.0
    Fixed in
    0.30.0

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.1 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
EPSS
  • CVE-2026-105752: 0.22% estimated exploitation activity in the next 30 days; percentile 12.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Affected - Ecosystem / package: pip / vllm - Affected versions: vLLM ≤ 0.25.1 (confirmed on 0.25.1, commit 752a3a504485). The lower bound predates 0.25.1; maintainers can confirm how far back the tool-continuation re-submission has omitted the salt. Summary On the GPT-OSS "Harmony" path (POST /v1/responses), a request that uses a built-in or MCP tool runs as a multi-turn loop: after each tool call vLLM re-renders the full next-turn Harmony prompt and re-submits it to the engine. Turn 1 correctly carries request.cachesalt, but the tool-continuation re-submission rebuilds the engine input via tokensinput(tokenids) with no cachesalt. The continuation prefix is therefore cached in the global unsalted namespace even though the caller opted into salting. A second tenant who can guess the low-entropy post-tool history submits the reconstructed continuation (unsalted) and reads exact per-turn cached-token counts from the Responses usage — restoring the prompt-membership oracle that cachesalt…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-935w-9g4m-p28p

  2. Revision 2 · amended ·

    Amended from osv record GHSA-935w-9g4m-p28p

  3. Revision 1 · created ·

    Published from ghsa record GHSA-935w-9g4m-p28p

Agent brief

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# Patch Next advisory brief: CVE-2026-105752

Advisory: vLLM: Harmony tool continuations drop `cache_salt` — restoring a cross-tenant prefix-cache membership oracle
IDs: CVE-2026-105752, GHSA-935w-9g4m-p28p
Record: https://patchnext.com/advisories/cve-2026-105752 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vllm 0.30.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI vllm: affected < 0.30.0; fixed in 0.30.0

## Suggested inspection (read-only)
- `python -m pip show vllm`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on vllm.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-935w-9g4m-p28p (GitHub-reviewed advisory GHSA-935w-9g4m-p28p lists affected ranges: PyPI vllm >=0 <0.30.0)
- Verified: https://osv.dev/vulnerability/GHSA-935w-9g4m-p28p (OSV record GHSA-935w-9g4m-p28p lists affected ranges: PyPI vllm >=0 <0.30.0 (fixed))

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