CVE-2026-34983Public exploit

Embedding-process crash via dangling cloned string keys

Published Apr 9, 2026 · Updated Apr 9, 2026

Use-after-free in Wasmtime 43.0.0 allows local users controlling host API calls to crash an embedding process through Linker cloning. StringPool::try_clone copies map keys that reference the original pool's string storage, leaving dangling keys after the original Linker is dropped. Guest Wasm and the CLI cannot reach the flaw; the host must clone a Linker, drop the original, and use the clone, and the reported consequence is a segfault without heap corruption or data leakage.

CVSS severity1.0
Low
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Wasmtime 43.0.0 allows local users controlling host API calls to crash an embedding process through Linker cloning. StringPool::try_clone copies map keys that reference the original pool's string storage, leaving dangling keys after the original Linker is dropped. Guest Wasm and the CLI cannot reach the flaw; the host must clone a Linker, drop the original, and use the clone, and the reported consequence is a segfault without heap corruption or data leakage.

The record

CVE
CVE-2026-34983
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-416
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 43.0.0, < 43.0.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Bytecode Alliance · Wasmtimeversion=>= 43.0.0, < 43.0.1

Published CVSS scores

5.0NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
1.0GitHubCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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