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Vulnerabilities

Vulnerability · CVE-2026-34983

Wasmtime is a runtime for WebAssembly.

Published Apr 9, 2026 · catalog updated Jun 17, 2026 · Wasmtime is a runtime

Check if you run it

No confirmed exploitation is on record for CVE-2026-34983. EPSS is 0.12%. Act only if a listed version of Wasmtime is a runtime is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Wasmtime is a runtime).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Low1.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.12%
Remediation
Advisory link
Affected products
cpe bytecodealliance/wasmtime

Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the new, cloned linker instance, resulting in a use-after-free. This vulnerability is fixed in 43.0.1.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe bytecodealliance/wasmtime43.0.0

How to fix CVE-2026-34983

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-34983. EPSS is 0.12%. Act only if a listed version of Wasmtime is a runtime is installed.

Which versions are affected?

Compare what you have installed with 43.0.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-416: Use After Free. EPSS 0.12%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 9, 2026 · NIST NVD

    Detected

    Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the

  2. Jun 17, 2026 · NIST NVD

    Updated

    Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the

Sources

  • CVE.orgVulnerability recordCVE-2026-34983

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-34983

    30-day exploitation probability 0.1%

    first.org
  • NIST NVDVulnerability recordCVE-2026-34983

    Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.