CVE-2026-121440

Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 Forwarded Trailers Header Filter Bypass

CVSS 4.0 6.3 MEDIUMCVSS 3.1 3.7 LOWEUVD CVSS 4.0 6.3 CVSS 4.0 · [email protected] · Secondary 6.3 MEDIUMCVSS 3.1 · [email protected] · Secondary 3.7 LOWCVSS_V3 Fixed by wasmtime-wasi-http 48.0.7 Fixed by wasmtime-wasi-http 49.0.4KEV status unknown

Original advisory

cve-program · CVE-2026-121440

Published

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.

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euvd · EUVD-2026-115862

Published

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nvd · CVE-2026-121440

Published

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osv · RUSTSEC-2026-0377

Published

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-jxcf-8qw5-5c33 For more information see the GitHub-hosted security advisory.

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Affected versions, risk and source history

cve-program · CVE-2026-121440

Published

wasmtime

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "bytecodealliance",
                    "product": "wasmtime",
                    "defaultStatus": "unaffected",
                    "packageURL": "pkg:cargo/wasmtime-wasi-http",
                    "versions": [
                        {
                            "version": "46.0.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "48.0.7"
                        },
                        {
                            "version": "48.0.7",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "49.0.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "49.0.4"
                        },
                        {
                            "version": "49.0.4",
                            "status": "unaffected",
                            "versionType": "semver"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON

euvd · EUVD-2026-115862

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Nov 3, 2026, 2:28:31 PM

dateUpdated: Nov 3, 2026, 6:28:48 PM

No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.

Original source record · Cite this exact observation · Complete original publisher JSON

nvd · CVE-2026-121440

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Deferred

Weakness classifications: CWE-424

Original publisher date fields

published: 2026-11-03T15:17:35.707

lastModified: 2026-11-03T19:18:03.383

Original source record · Cite this exact observation · Complete original publisher JSON

osv · RUSTSEC-2026-0377

Published

wasmtime-wasi-http

crates.io

SEMVER · introduced 46.0.0 → fixed 48.0.7 → introduced 49.0.0 → fixed 49.0.4

Original source record · Cite this exact observation · Complete original publisher JSON