{"answers":{"affected":"7 open source packages ship an affected version, including wasmtime. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-34987 in the wild and no public exploit code.","fix":"Upgrade wasmtime to a fixed version for your release line: 36.0.7, 42.0.2 or 43.0.1.","what":"CVE-2026-34987 is a critical memory corruption vulnerability in bytecodealliance wasmtime, published on 9 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-34987 and fix it if it is affected.\n\nWhat it is: CVE-2026-34987 is a critical memory corruption vulnerability in bytecodealliance wasmtime, published on 9 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-34987 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- wasmtime (crates.io): affected from 0.0.0-0; fixed in 36.0.7, 42.0.2, 43.0.1\n- wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.7\n- wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.7\n- wasmtime (crates.io): affected from 37.0.0; fixed in 42.0.2\n- wasmtime (crates.io): affected from 37.0.0; fixed in 42.0.2\n- wasmtime (crates.io): affected from 43.0.0; fixed in 43.0.1\n- wasmtime (crates.io): affected from 43.0.0; fixed in 43.0.1\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-34987/ (Markdown: https://insights.sbomify.com/CVE-2026-34987/index.md)","id":"CVE-2026-34987","markdown":"https://insights.sbomify.com/CVE-2026-34987/index.md","name":"CVE-2026-34987","record":{"aliases":["DEBIAN-CVE-2026-34987","GHSA-xx5w-cvp6-jv83","JLSEC-2026-1361","RUSTSEC-2026-0095","UBUNTU-CVE-2026-34987"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["code_execution","data_read","denial_of_service"],"network_reachable":"yes","non_default_config":true,"product_category":"WebAssembly runtime","requires_auth":"low_privilege","summary":"A memory corruption flaw in Wasmtime's Winch compiler on aarch64 allows sandbox escape, potentially leading to arbitrary code execution or data leaks.","user_interaction":"not_required","vuln_class":"memory_corruption"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"wasmtime","vendor":"bytecodealliance"}],"cvss":{"score":9,"severity":"critical","source":"cna","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","version":"4.0"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"},{"id":"CWE-125","name":"Out-of-bounds Read"}],"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.","ecosystems":["crates.io"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","id":"CVE-2026-34987","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"crates.io","product":null,"products":[],"type":"memory_corruption","year":"2026"},"n_packages":7,"n_references":1,"next":{"headline":"Wasmtime leaks data between pooling allocator instances","id":"CVE-2026-34988"},"packages":[{"ecosystem":"crates.io","fixed":["36.0.7","42.0.2","43.0.1"],"introduced":["0.0.0-0","37.0.0","43.0.0"],"last_affected":[],"package":"wasmtime","purl":"pkg:cargo/wasmtime","source":"RUSTSEC-2026-0095"},{"ecosystem":"crates.io","fixed":["36.0.7"],"introduced":["25.0.0"],"last_affected":[],"package":"wasmtime","purl":null,"source":"GHSA-xx5w-cvp6-jv83"},{"ecosystem":"crates.io","fixed":["36.0.7"],"introduced":["25.0.0"],"last_affected":[],"package":"wasmtime","purl":"pkg:cargo/wasmtime","source":"GHSA-xx5w-cvp6-jv83"},{"ecosystem":"crates.io","fixed":["42.0.2"],"introduced":["37.0.0"],"last_affected":[],"package":"wasmtime","purl":null,"source":"GHSA-xx5w-cvp6-jv83"},{"ecosystem":"crates.io","fixed":["42.0.2"],"introduced":["37.0.0"],"last_affected":[],"package":"wasmtime","purl":"pkg:cargo/wasmtime","source":"GHSA-xx5w-cvp6-jv83"},{"ecosystem":"crates.io","fixed":["43.0.1"],"introduced":["43.0.0"],"last_affected":[],"package":"wasmtime","purl":null,"source":"GHSA-xx5w-cvp6-jv83"},{"ecosystem":"crates.io","fixed":["43.0.1"],"introduced":["43.0.0"],"last_affected":[],"package":"wasmtime","purl":"pkg:cargo/wasmtime","source":"GHSA-xx5w-cvp6-jv83"}],"prev":{"headline":"Go JOSE affect by a panic in JWE decryption","id":"CVE-2026-34986"},"products":["wasmtime"],"published":"2026-04-09","related":[{"cvss_score":9,"headline":"Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift","id":"CVE-2026-34971","kev_date_added":null,"published":"2026-04-09"},{"cvss_score":8.6,"headline":"Wasmtime vulnerable to data leakage between instances in the pooling allocator","id":"CVE-2022-39393","kev_date_added":null,"published":"2022-11-10"},{"cvss_score":8.1,"headline":"Use after free in Wasmtime","id":"CVE-2022-24791","kev_date_added":null,"published":"2022-03-31"},{"cvss_score":7.5,"headline":"Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction","id":"CVE-2026-47261","kev_date_added":null,"published":"2026-06-15"},{"cvss_score":6.9,"headline":"Wasmtime has a Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding","id":"CVE-2026-34941","kev_date_added":null,"published":"2026-04-09"},{"cvss_score":6.9,"headline":"Wasmtime is vulnerable to panic when dropping a `[Typed]Func::call_async` future","id":"CVE-2026-27195","kev_date_added":null,"published":"2026-02-24"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"open","licence":"CC0 1.0","name":"RustSec","prefix":"RUSTSEC"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-04-10","vendors":["bytecodealliance"]},"summary":"A memory corruption flaw in Wasmtime's Winch compiler on aarch64 allows sandbox escape, potentially leading to arbitrary code execution or data leaks.","url":"https://insights.sbomify.com/CVE-2026-34987/"}