CVE-2026-34983: CWE-416: Use After Free in 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.
AI Analysis
Technical Summary
Wasmtime 43.0.0 contains a use-after-free vulnerability (CWE-416) triggered by cloning a wasmtime::Linker, dropping the original, and then using the clone. This bug is not exploitable by guest WebAssembly code but only through a particular sequence of host API calls. The issue is resolved in wasmtime 43.0.1.
Potential Impact
The vulnerability can cause use-after-free memory corruption when the host application clones and uses wasmtime::Linker instances in an unsound manner. Since guest Wasm programs cannot trigger this, the impact is limited to host applications embedding wasmtime. No known exploits exist in the wild, and the CVSS score is low, indicating limited risk.
Mitigation Recommendations
Upgrade to wasmtime version 43.0.1 or later, where this use-after-free vulnerability is fixed. Since this is a library-level bug triggered by host API misuse, applying the official patch is the recommended remediation.
CVE-2026-34983: CWE-416: Use After Free in bytecodealliance wasmtime
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Wasmtime 43.0.0 contains a use-after-free vulnerability (CWE-416) triggered by cloning a wasmtime::Linker, dropping the original, and then using the clone. This bug is not exploitable by guest WebAssembly code but only through a particular sequence of host API calls. The issue is resolved in wasmtime 43.0.1.
Potential Impact
The vulnerability can cause use-after-free memory corruption when the host application clones and uses wasmtime::Linker instances in an unsound manner. Since guest Wasm programs cannot trigger this, the impact is limited to host applications embedding wasmtime. No known exploits exist in the wild, and the CVSS score is low, indicating limited risk.
Mitigation Recommendations
Upgrade to wasmtime version 43.0.1 or later, where this use-after-free vulnerability is fixed. Since this is a library-level bug triggered by host API misuse, applying the official patch is the recommended remediation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-31T19:38:31.617Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7f88c1cc7ad14da0c1703
Added to database: 4/9/2026, 7:05:48 PM
Last enriched: 4/17/2026, 12:01:20 PM
Last updated: 5/25/2026, 2:40:49 AM
Views: 47
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