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CVE-2026-34983— Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`

Quick assessment

Affected
bytecodealliance wasmtime
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

wasmtime是Bytecode Alliance开源的一个轻量级WebAssembly运行时。 Wasmtime 43.0.0版本存在资源管理错误漏洞，该漏洞源于克隆wasmtime::Linker时存在缺陷，可能导致释放后重用。

AI Predicted 4.4 Difficulty: Moderate EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth
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I. Basic Information for CVE-2026-34983

Vulnerability Information
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Vulnerability Title
Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
wasmtime 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
wasmtime是Bytecode Alliance开源的一个轻量级WebAssembly运行时。 Wasmtime 43.0.0版本存在资源管理错误漏洞，该漏洞源于克隆wasmtime::Linker时存在缺陷，可能导致释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
bytecodealliance wasmtime >= 43.0.0, < 43.0.1 -

II. Public POCs for CVE-2026-34983

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III. Intelligence Information for CVE-2026-34983

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Vendor Advisories for CVE-2026-34983 (1)

Same Patch Batch · bytecodealliance · 2026-04-09 · 12 CVEs total

CVE-2026-35195 Wasmtime has an out-of-bounds write or crash when transcoding component model strings
CVE-2026-35186 Wasmtime has an improperly masked return value from `table.grow` with Winch compiler backe
CVE-2026-34941 Wasmtime has a Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding
CVE-2026-34942 Wasmtime panics when transcoding misaligned utf-16 strings
CVE-2026-34988 Wasmtime leaks data between pooling allocator instances
CVE-2026-34971 Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift
CVE-2026-34946 Wasmtime's host panics when Winch compiler executes `table.fill`
CVE-2026-34944 Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
CVE-2026-34945 Wasmtime leaks host data with 64-bit tables and Winch
CVE-2026-34987 Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access
CVE-2026-34943 Wasmtime panics when lifting `flags` component value

IV. Related Vulnerabilities

Same product: wasmtime
Same vendor: bytecodealliance
Same weakness: CWE-416

V. Comments for CVE-2026-34983

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