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Response snapshot Oct 27, 2026, 01:06 UTC

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VulnerabilityCVE-2026-115892

Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type

Wasmtime may panic when the host lowers a component model `stream` or `future` into a guest, if the host created that stream or future with one payload type and the guest expects a different one.

At a glance

Exploited
Not known
Severity
5.7 Medium (CVSS 4.0)
Chance of exploitation
0.4% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: wasmtime: 48.0.7; wasmtime: 49.0.4. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-9pvw-hwfg-92h5 (opens a new tab)

What happened

### Summary

Wasmtime may panic when the host lowers a component model `stream` or `future` into a guest, if the host created that stream or future with one payload type and the guest expects a different one. This can happen when an embedder creates a stream or future, passes it through a guest, receives it back under a type-erased type such as `StreamAny` or `FutureAny`, and then passes it to a guest function with a different payload type.

GHSA-63h4-6cx9-pjfj is a related advisory also fixing issues within this area, and this advisory is being issued for portions of Wasmtime that were not fixed as part of that advisory.

### Impact

Continue reading

This affects embedders that do all of the following:

1. Create streams or futures on the host with `StreamReader::new` or `FutureReader::new` 2. Pass them to guest code and receive them back as `StreamAny`, `FutureAny`, `Val::Stream`/`Val::Future`, or a typed reader whose payload is one of these. 3. Pass them on to a guest function whose `stream` or `future` payload type differs from the type the host created them with.

A guest can cause the mismatch in step 3 when it controls the types of the functions it exports or of the values it returns. In that case a malicious guest can make the host panic, a denial of service. Embedders that only use statically typed `StreamReader `/`FutureReader ` with concrete payload types throughout, or that never pass streams or futures they created through a guest and back, are not affected.

Affected package ranges reported by GitHub: wasmtime: >= 46.0.0, < 48.0.7 wasmtime: >= 49.0.0, < 49.0.4

Scores and how they were measured

CVSS base severity

5.7

Version 4.0As of

CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 37.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-9pvw-hwfg-92h5 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9pvw-hwfg-92h5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-115892, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type (CVE-2026-115892). https://kevwire.com/record/CVE-2026-115892

MLA

"Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type (CVE-2026-115892)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-115892.

Chicago

KEVWire. "Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type (CVE-2026-115892)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-115892.

Evidence summary (plain text)

Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type (Oct 23, 2026).
Wasmtime may panic when the host lowers a component model `stream` or `future` into a guest, if the host created that stream or future with one payload type and the guest expects a different one. This can happen when an embedder creates a stream or future, passes it through a guest, receives it back under a type-erased type such as `StreamAny` or `FutureAny`, and then passes it to a guest function with a different payload type.

GHSA-63h4-6cx9-pjfj is a related advisory also fixing issues within this area, and this advisory is being issued for portions of Wasmtime that were not fixed as part of that advisory.
CVSS 5.7 (version 4.0; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-9pvw-hwfg-92h5).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-115892&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-9pvw-hwfg-92h5: https://github.com/advisories/GHSA-9pvw-hwfg-92h5
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-115892&date=2026-10-26
Record ID: CVE-2026-115892.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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