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CVE-2026-121441— Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling

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 在以下版本中存在请求走私（request smuggling）漏洞：36.0.19 之前的版本、37.0.0 至 48.0.7 之前的版本，以及 49.0.0 至 49.0.4 之前的版本。该漏洞位于 wasi-http 组件中，允许 guest（客户机）设置多个相互冲突的 Content-Length 头。恶意 guest 可利用此漏洞，促使 host（主机）向服务器或中间代理发送包含冲突 Content-Length 值的 HTTP 请求，从而绕过那些未明确拒绝此类请求的服务器或中间设备，实现

CVSS 3.7 · Low
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I. Basic Information for CVE-2026-121441

Vulnerability Information
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Vulnerability Title
Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling
Source: CVE Program / CVE List V5
Vulnerability Description
Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 contains a request smuggling vulnerability in wasi-http that allows guests to set multiple conflicting content-length headers. Malicious guests can make the host send HTTP requests with conflicting content-length values to smuggle requests through servers or intermediaries that do not reject them.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
bytecodealliance wasmtime 0 ~ 36.0.19 -

II. Public POCs for CVE-2026-121441

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III. Intelligence Information for CVE-2026-121441

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Other References for CVE-2026-121441 (2)

Same Patch Batch · bytecodealliance · 2026-11-03 · 3 CVEs total

CVE-2026-121439 5.3 MEDIUM Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 HTTP Response Splitting via wasi-ht
CVE-2026-121440 3.7 LOW Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 Forwarded Trailers Header Filter By

IV. Related Vulnerabilities

Same product: wasmtime
Same vendor: bytecodealliance
Same weakness: CWE-444