Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling
- Exploited
- No known exploitation
- Fix
- Fixed in 36.0.19, 48.0.7, 49.0.4
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 36.0.19, 48.0.7, 49.0.4.
- Exploitation0/40No signal
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Data gap: No advisory context yet
- Reach10/20Affects crates.io packages
- Severity6.3/10CVSS 6.3
- No patch0/5No signal
What would change the score
- Would score about 78 if added to CISA KEV
- Would score about 73 if CISA's SSVC rates exploitation active
- Would score about 38 if advisories confirm default setups are exposed
CVE-2026-121441 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.3 (medium) and affects wasmtime; fixed in 36.0.19, 48.0.7 and 49.0.4.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 33/100 · provisional
- Fix
- Fixed in 36.0.19, 48.0.7, 49.0.4
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
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.
What to do
Upgrade to a fixed version: 36.0.19, 48.0.7, 49.0.4.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- bytecodealliance wasmtime
fixed in 36.0.19; From 37.0.0 · fixed in 48.0.7; From 49.0.0 · fixed in 49.0.4
- wasmtime-wasi-httpcrates.io
From 0.0.0-0 · fixed in 36.0.19; From 37.0.0 · fixed in 48.0.7; From 49.0.0 · fixed in 49.0.4
Evidence 2
- Advisory
- Link
Corrections
None so far.
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Questions about CVE-2026-121441
Is CVE-2026-121441 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-121441?
wasmtime: before 36.0.19; from 37.0.0 before 48.0.7; from 49.0.0 before 49.0.4. wasmtime-wasi-http (crates.io): from 0.0.0-0 before 36.0.19; from 37.0.0 before 48.0.7; from 49.0.0 before 49.0.4.Source: cve.now feed data
How do I fix CVE-2026-121441?
Upgrade to a fixed version: 36.0.19, 48.0.7, 49.0.4.Source: cve.now feed data