PT-2026-31689 · Bytecode Alliance · Wasmtime

Published 2026-04-09 · Updated 2026-04-09 · CVE-2026-34983

Positive Technologies (AI Summary)

CVSS v3.1

5.0

Medium

Base vector

AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions Wasmtime versions 43.0.0 through 43.0.0

Description Wasmtime, a runtime for WebAssembly, contains a flaw where cloning a wasmtime::Linker can lead to use-after-free bugs. This issue is not triggered by guest Wasm programs but requires a specific sequence of host embedder API calls. The vulnerability occurs when a wasmtime::Linker is cloned, the original instance is dropped, and the cloned instance is subsequently used. This can result in a segfault. The issue was introduced during an internal refactoring related to robust allocation failure handling and a string-interning pool with an unsound TryClone implementation.

Recommendations Upgrade to Wasmtime version 43.0.1. As a temporary workaround, avoid cloning wasmtime::Linker and instead create a new wasmtime::Linker and manually reregister the host APIs from the original linker.

Exploit

Fix

Use After Free

Weakness Enumeration

CWE-416

Related Identifiers

CVE-2026-34983

GHSA-HFR4-7C6C-48W2

PYSEC-2026-151

RUSTSEC-2026-0090

Affected Products

Wasmtime

References · 16

• 🔥 https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2 · Exploit
• https://ubuntu.com/security/CVE-2026-34983 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-34983 · Security Note
• https://osv.dev/vulnerability/GHSA-hfr4-7c6c-48w2 · Vendor Advisory
• https://osv.dev/vulnerability/RUSTSEC-2026-0090 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-34983 · Vendor Advisory
• https://osv.dev/vulnerability/PYSEC-2026-151 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-34983 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-34983 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-34983 · Security Note
• https://github.com/bytecodealliance/wasmtime · Note
• https://github.com/pypa/advisory-database/tree/main/vulns/wasmtime/PYSEC-2026-151.yaml · Note
• https://twitter.com/infoflowcloud/status/2042340842619253162 · Twitter Post
• https://twitter.com/CVEnew/status/2042340082833596594 · Twitter Post
• https://rustsec.org/advisories/RUSTSEC-2026-0090.html · Note