{"id":"JLSEC-2026-1355","summary":"Wasmtime: Panic when transcoding misaligned utf-16 strings","details":"### Impact\n\nWasmtime's implementation of transcoding strings into the Component Model's `utf16` or `latin1+utf16` encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses.\n\nHost panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation.\n\n### Patches\n\nWasmtime 24.0.7, 36.0.7, 42.0.2, and 43.0.1 have been issued to fix this bug. Users are recommended to update to these patched versions of Wasmtime.\n\n### Workarounds\n\nThere is no workaround for this bug. Hosts are recommended to updated to a patched version of Wasmtime.","modified":"2026-08-21T21:14:22.065104343Z","published":"2026-08-21T20:43:33.133Z","upstream":["CVE-2026-34942","EUVD-2026-20990","GHSA-jxhv-7h78-9775"],"database_specific":{"license":"CC-BY-4.0","sources":[{"affected":{"bytecodealliance:wasmtime":["\u003c 24.0.7","\u003e= 25.0.0, \u003c 36.0.7","\u003e= 37.0.0, \u003c 42.0.2","\u003e= 43.0.0, \u003c 43.0.1"]},"id":"CVE-2026-34942","imported":"2026-08-21T20:09:02.076Z","modified":"2026-06-17T10:39:51.497Z","published":"2026-04-09T19:16:23.857Z","url":"https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34942","html_url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34942","database_specific":{"status":"Analyzed"}},{"url":"https://api.github.com/advisories/GHSA-jxhv-7h78-9775","html_url":"https://github.com/advisories/GHSA-jxhv-7h78-9775","id":"GHSA-jxhv-7h78-9775","imported":"2026-08-21T20:09:13.967Z","modified":"2026-04-24T21:03:48Z","published":"2026-04-09T20:22:12Z"},{"published":"2026-04-09T18:32:56Z","url":"https://euvdservices.enisa.europa.eu/api/enisaid?id=EUVD-2026-20990","html_url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-20990","affected":{"bytecodealliance:wasmtime":["25.0.0, \u003c 36.0.7","37.0.0, \u003c 42.0.2","43.0.0, \u003c 44.0.1","\u003c 24.0.7"]},"id":"EUVD-2026-20990","imported":"2026-08-21T20:09:03.523Z","modified":"2026-04-09T19:36:13Z"}]},"references":[{"type":"WEB","url":"https://github.com/advisories/GHSA-jxhv-7h78-9775"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-jxhv-7h78-9775"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34942"},{"type":"WEB","url":"https://rustsec.org/advisories/RUSTSEC-2026-0092.html"}],"affected":[{"package":{"name":"Wasmtime_jll","ecosystem":"Julia","purl":"pkg:julia/Wasmtime_jll?uuid=d20e7296-4f3e-515c-90b9-d2595a77bf72"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"45.0.1+0"}]}],"database_specific":{"source":"https://github.com/JuliaLang/SecurityAdvisories.jl/tree/generated/osv/2026/JLSEC-2026-1355.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"}],"credits":[{"name":"alexcrichton","contact":["https://github.com/alexcrichton"],"type":"OTHER"}]}