# \`wasi-http\` p3: Guests can set incorrect content-length for spliced response bodies

Advisory record · `GHSA-9prg-84vf-g5fc`

- **Identifiers:** `GHSA-9prg-84vf-g5fc` · `CVE-2026-121439` · `RUSTSEC-2026-0375`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-444](https://cwe.mitre.org/data/definitions/444.html)
- **Tags:** [HTTP request smuggling](https://agentprime.io/advisories/tag/request-smuggling.md)
- **Published:** 19 Oct 2026
- **Updated:** 4 Nov 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 19 Oct 2026, 12:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `wasmtime-wasi-http` (crates.io): affected `>=46.0.0, <48.0.7 || >=49.0.0, <49.0.4`; fixed in `48.0.7`, `49.0.4`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The wasmtime-wasi-http crate is vulnerable in versions 46.0.0 up to 48.0.7 and 49.0.0 up to 49.0.4. A guest component can set an incorrect content-length on spliced response bodies, which is a MEDIUM severity issue (CVSS 5.3). The source gives few details beyond this, and no attack requirements or impacts are described. Upgrade to version 48.0.7 or 49.0.4.

Written 3 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.9 Medium, CVSS 4.0: `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`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0019, the 9th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:24 UTC: First seen by agentprime
- 31 Oct 2026, 14:24 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/RUSTSEC-2026-0375)
- 3 Nov 2026, 14:38 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-121439)
- 3 Nov 2026, 15:25 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-121439)

## Sources

- [GitHub Advisory Database: GHSA-9prg-84vf-g5fc](https://github.com/advisories/GHSA-9prg-84vf-g5fc)
- [OSV: GHSA-9prg-84vf-g5fc](https://osv.dev/vulnerability/GHSA-9prg-84vf-g5fc)
- <https://crates.io/crates/wasmtime-wasi-http>
- <https://rustsec.org/advisories/RUSTSEC-2026-0375.html>
- <https://github.com/bytecodealliance/wasmtime/pull/14822>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-9prg-84vf-g5fc>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-9prg-84vf-g5fc/>. Everything for agents: <https://agentprime.io/llms.txt>.