Medium · CVSS 6.3CVE-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 SmugglingCVE-2026-121441

Answer in brief

CVE-2026-121441 records a Medium severity (CVSS 6.3) vulnerability in Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling. The current sources do not mark it as known exploited. The current feed maps bytecodealliance/wasmtime (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Nov 3, 2026Updated Nov 3, 2026Source checked Nov 3, 2026First seen by HOL Nov 3, 2026Material review Nov 3, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps bytecodealliance/wasmtime (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
bytecodealliance/wasmtimegeneric	>=0 <36.0.19 \|\| >=37.0.0 <48.0.7 \|\| >=49.0.0 <49.0.4	36.0.19, 48.0.7, 49.0.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for bytecodealliance/wasmtime.
Review the reported fix. Update bytecodealliance/wasmtime to 36.0.19 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Nov 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Nov 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Nov 3, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.