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Low, CVSS 2.3

Wasmtime has data leakage between pooling allocator instances

CVE-2026-34988GHSA-6wgr-89rj-399p

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (wasmtime 43.0.1, 42.0.2, 36.0.7), 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

  • crates.io wasmtime

    Affected
    >= 28.0.0, < 36.0.7>= 37.0.0, < 42.0.2>= 43.0.0, <= 43.0.0
    Fixed in
    36.0.7, 43.0.1, 42.0.2

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
2.3 · CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N · score source
EPSS
  • CVE-2026-34988: 0.29% estimated exploitation activity in the next 30 days; percentile 21.20 (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.

Impact Wasmtime's implementation of its pooling allocator contains a bug where in certain configurations the contents of linear memory can be leaked from one instance to the next. The implementation of resetting the virtual memory permissions for linear memory used the wrong predicate to determine if resetting was necessary, where the compilation process used a different predicate. This divergence meant that the pooling allocator incorrectly deduced at runtime that resetting virtual memory permissions was not necessary while compile-time determine that virtual memory could be relied upon. Exposing this bug requires specific configuration values to be used. If any of these configurations are not applicable then this bug does not happen: The pooling allocator must be in use. The Config::memoryguardsize configuration option must be 0. The Config::memoryreservation configuration must be less than 4GiB. The pooling allocator must be configured with maxmemorysize the same as the…

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

    Published from ghsa record GHSA-6wgr-89rj-399p

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-34988

Advisory: Wasmtime has data leakage between pooling allocator instances
IDs: CVE-2026-34988, GHSA-6wgr-89rj-399p
Record: https://patchnext.com/advisories/cve-2026-34988 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: wasmtime 43.0.1, 42.0.2, 36.0.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io wasmtime: affected >= 28.0.0, < 36.0.7; >= 37.0.0, < 42.0.2; >= 43.0.0, <= 43.0.0; fixed in 36.0.7, 43.0.1, 42.0.2

## Suggested inspection (read-only)
- crates.io wasmtime: check the installed version with your package manager.

## 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 wasmtime.
- 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-6wgr-89rj-399p (GitHub-reviewed advisory GHSA-6wgr-89rj-399p lists affected ranges: crates.io wasmtime >=28.0.0 =37.0.0 =43.0.0 <=43.0.0)

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