6.9
/ 10
MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Description
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte length, which is twice the size of the code units. This vulnerability can cause the host to read beyond the end of a WebAssembly's linear memory in an attempt to transcode nonexistent bytes. In Wasmtime's default configuration this will read unmapped memory on a guard page, terminating the process with a segfault. Wasmtime can be configured, however, without guard pages which would mean that host memory beyond the end of linear memory may be read and interpreted as UTF-16. A host segfault is a denial-of-service vulnerability in Wasmtime, and possibly being able to read beyond the end of linear memory is additionally a vulnerability. Note that reading beyond the end of linear memory requires nonstandard configuration of Wasmtime, specifically with guard pages disabled. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Basic Information
ID
CVE-2026-34941
Source
GitHub_M
Published
Apr 9, 2026 at 18:29
Modified
Apr 10, 2026 at 14:11
Affected Product
Vendor
bytecodealliance
Product
wasmtime
Version
< 24.0.7
Affected Versions
bytecodealliance wasmtime < 24.0.7
bytecodealliance wasmtime >= 25.0.0, < 36.0.7
bytecodealliance wasmtime >= 37.0.0, < 42.0.2
bytecodealliance wasmtime >= 43.0.0, < 44.0.1
bytecodealliance wasmtime >= 25.0.0, < 36.0.7
bytecodealliance wasmtime >= 37.0.0, < 42.0.2
bytecodealliance wasmtime >= 43.0.0, < 44.0.1