{"id":"EUVD-2026-21031","revision":"b94fa03fb46e4f92a61db5edad154487","records":[{"revision":"b94fa03fb46e4f92a61db5edad154487","observedAt":"2026-10-30T05:52:09.015+00:00","statement":{"source":"euvd","id":"EUVD-2026-21031","aliases":["CVE-2026-34987","GHSA-xx5w-cvp6-jv83"],"title":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-m…","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","score":9,"severity":null}],"references":["https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-21031","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Apr 9, 2026, 6:48:33 PM","dateUpdated":"Apr 10, 2026, 2:12:55 PM"},"relatedAdvisories":[{"id":"SUSE-SU-2026:21789-1","title":"Security update for tree-sitter","vulnerabilityIds":["CVE-2026-34941","CVE-2026-34942","CVE-2026-34943","CVE-2026-34944","CVE-2026-34945","CVE-2026-34946","CVE-2026-34987","CVE-2026-34988","CVE-2026-35186","CVE-2026-35195"]},{"id":"openSUSE-SU-2026:20749-1","title":"Security update for tree-sitter","vulnerabilityIds":["CVE-2026-34941","CVE-2026-34942","CVE-2026-34943","CVE-2026-34944","CVE-2026-34945","CVE-2026-34946","CVE-2026-34987","CVE-2026-34988","CVE-2026-35186","CVE-2026-35195"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-21031","identifiers":["EUVD-2026-21031","CVE-2026-34987","GHSA-xx5w-cvp6-jv83"]},"retained":false,"historicalAffected":[]}],"coverage":[]}