Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-121440— Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 Forwarded Trailers Header Filter Bypass

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.

在 Wasmtime 46.0.0 至 48.0.7 之前的版本，以及 49.0.0 至 49.0.4 之前的版本中，wasi-http p3 未能针对转发的尾部（trailers）检查 钩子。这导致 WASIp3 客人程序（guest）可以转发请求或响应主体，使其尾部绕过由宿主（embedder）自定义的禁止头部过滤机制，从而破坏了宿主原本旨在实施的头部限制。

CVSS 3.7 · Low

Possible ATT&CK Techniques 1 AI

T1069.001 · Local Groups

Affected Version Matrix 4

VendorProduct Version RangeStatus
bytecodealliance wasmtime 46.0.0< 48.0.7 affected
48.0.7 unaffected
49.0.0< 49.0.4 affected
49.0.4 unaffected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-121440

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 Forwarded Trailers Header Filter Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 fails to check forwarded trailers against the WasiHttpHooks::is_forbidden_header hook in wasi-http p3. WASIp3 guests can forward a request or response body so its trailers skip embedder-customized forbidden header filtering, undermining header restrictions the embedder intended.
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
对候选路径的不恰当保护
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
bytecodealliance wasmtime 46.0.0 ~ 48.0.7 -

II. Public POCs for CVE-2026-121440

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-121440

请登录查看更多情报信息。

Other References for CVE-2026-121440 (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-2026-121441 3.7 LOW Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request

IV. Related Vulnerabilities

Same product: wasmtime
Same vendor: bytecodealliance
Same weakness: CWE-424