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CVE-2026-121439

6.9 mediumEPSS 0.2%

Medium (6.9). EPSS 0.2% estimated probability of exploitation activity in the next 30 days. Fixed in wasmtime-wasi-http 48.0.7, 49.0.4.

On this page
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 contains a response splitting vulnerability in wasi-http p3 that allows guests to set unvalidated content-length headers. Malicious wasip3 guests can splice an existing body into a new response with an incorrect content-length to perform response splitting or injection attacks.

Severity

CVSS 4.0

6.9 medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

5.3 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS
0.2% estimated probability of exploitation activity in the next 30 days; 9th percentile. Scored 2026-11-04. A forecast for this CVE across the internet, not for your own systems.
CWE
CWE-444 Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling)
OWASP Top 10
A06:2025 Insecure Design
Published
Modified
Record from
the NVD, synced

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Versions

From the CNA's record in the CVE List.

ProductAffected
bytecodealliance wasmtimefrom 46.0.0 before 48.0.7
bytecodealliance wasmtimefrom 49.0.0 before 49.0.4

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
RUSTSEC-2026-0375crates.iowasmtime-wasi-http>=46.0.0 <48.0.7
>=49.0.0 <49.0.4		48.0.7, 49.0.4

Attack patterns (CAPEC)

  • CAPEC-33 HTTP Request Smuggling Likelihood: Medium · Severity: High
  • CAPEC-273 HTTP Response Smuggling Likelihood: Medium · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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