CVE-2026-121441

Low

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.

SeverityLow

CVSS3.7

Exploit probability—

ProductBytecodealliance Wasmtime

PublishedNov 3, 2026

First seenNov 4, 2026

Weakness typeCWE-444CWE-444

How to fix

Update

bytecodealliance wasmtime36.0.19, 48.0.7, 49.0.4 or later

Vendor advisories

github.com/bytecodealliance/wasmtime/security/advisories/GHSA-r8xh-cgf7-392j

Affected products

Product	Affected versions	Fixed in
bytecodealliance wasmtime	v < 36.0.19, 37.0.0 ≤ v < 48.0.7, 49.0.0 ≤ v < 49.0.4	36.0.19, 48.0.7, 49.0.4

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