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CVE-2026-34941— Wasmtime has a Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding

Quick assessment

Affected
bytecodealliance wasmtime
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

wasmtime是Bytecode Alliance开源的一个轻量级WebAssembly运行时。 Wasmtime 24.0.7之前版本、36.0.7之前版本、42.0.2之前版本和43.0.1之前版本存在缓冲区错误漏洞，该漏洞源于将UTF-16字符串转码为latin1+utf16组件模型编码时，执行边界检查错误地验证了输入字符串的代码单元数而非字节长度，可能导致主机尝试转码不存在的字节时读取超出WebAssembly线性内存的末尾，在默认配置下会因段错误终止进程，构成拒绝服务漏洞，在禁用保护页的非标准

AI Predicted 5.3 Difficulty: Moderate EPSS 0.46% · P38
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I. Basic Information for CVE-2026-34941

Vulnerability Information
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Vulnerability Title
Wasmtime has a Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
wasmtime 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
wasmtime是Bytecode Alliance开源的一个轻量级WebAssembly运行时。 Wasmtime 24.0.7之前版本、36.0.7之前版本、42.0.2之前版本和43.0.1之前版本存在缓冲区错误漏洞，该漏洞源于将UTF-16字符串转码为latin1+utf16组件模型编码时，执行边界检查错误地验证了输入字符串的代码单元数而非字节长度，可能导致主机尝试转码不存在的字节时读取超出WebAssembly线性内存的末尾，在默认配置下会因段错误终止进程，构成拒绝服务漏洞，在禁用保护页的非标准
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
bytecodealliance wasmtime < 24.0.7 -

II. Public POCs for CVE-2026-34941

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III. Intelligence Information for CVE-2026-34941

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Same Patch Batch · bytecodealliance · 2026-04-09 · 12 CVEs total

CVE-2026-35195 Wasmtime has an out-of-bounds write or crash when transcoding component model strings
CVE-2026-35186 Wasmtime has an improperly masked return value from `table.grow` with Winch compiler backe
CVE-2026-34983 Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`
CVE-2026-34942 Wasmtime panics when transcoding misaligned utf-16 strings
CVE-2026-34988 Wasmtime leaks data between pooling allocator instances
CVE-2026-34971 Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift
CVE-2026-34946 Wasmtime's host panics when Winch compiler executes `table.fill`
CVE-2026-34944 Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
CVE-2026-34945 Wasmtime leaks host data with 64-bit tables and Winch
CVE-2026-34987 Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access
CVE-2026-34943 Wasmtime panics when lifting `flags` component value

IV. Related Vulnerabilities

Same product: wasmtime
Same vendor: bytecodealliance
Same weakness: CWE-125

V. Comments for CVE-2026-34941

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