vLLM: Flash late-interaction scoring caches query embeddings under a caller-controlled request id — cross-request integrity break and induced errors on /score and /rerank

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.2 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L

EPSS

• CVE-2026-105755: 0.20% estimated exploitation activity in the next 30 days; percentile 10.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

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 flash late-interaction query cache reaches. Summary On late-interaction /score and /rerank deployments with flash late interaction enabled (the default for supported models), the worker caches per-request query embeddings under a key derived from the caller-controlled X-Request-Id header. A second concurrent request that reuses the victim's header value replaces the victim's cached query embedding before document scoring — so the victim's documents are scored against the attacker's query. Because the data-parallel router pins all requests sharing a cache key to the same engine, the collision is deterministic for an attacker who reuses the victim's X-Request-Id. Depending on timing, one request can also consume the shared use counter and force the other request into a late-interaction…

Published by the source

5 Oct 2026, 23:42 UTC

Last modified by the source

8 Oct 2026, 10:10 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2phq-3phc-84px

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-2phq-3phc-84px

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-2phq-3phc-84px

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# Patch Next advisory brief: CVE-2026-105755

Advisory: vLLM: Flash late-interaction scoring caches query embeddings under a caller-controlled request id — cross-request integrity break and induced errors on `/score` and `/rerank`
IDs: CVE-2026-105755, GHSA-2phq-3phc-84px
Record: https://patchnext.com/advisories/cve-2026-105755 (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: Medium (CVSS 4.2)
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-2phq-3phc-84px (GitHub-reviewed advisory GHSA-2phq-3phc-84px lists affected ranges: PyPI vllm >=0 <0.30.0)
- Verified: https://osv.dev/vulnerability/GHSA-2phq-3phc-84px (OSV record GHSA-2phq-3phc-84px lists affected ranges: PyPI vllm >=0 <0.30.0 (fixed))

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