# undici vulnerable to downstream response splitting via retry interceptor

Advisory record · `GHSA-r53p-7pc4-xj5r`

- **Identifiers:** `GHSA-r53p-7pc4-xj5r` · `CVE-2026-18540`
- **State:** Confirmed
- **Severity:** CVSS 3.7 Low
- **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:** 29 Sept 2026
- **Updated:** 29 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 29 Sept 2026, 18:22 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `undici` (npm): affected `<6.28.1 || >=7.0.0, <7.29.1 || >=8.0.0, <8.10.2`; fixed in `6.28.1`, `7.29.1`, `8.10.2`

## 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

- 3.7 Low, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N`, from CNA (openjs)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0031, the 23rd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 13:34 UTC: First seen by agentprime
- 31 Oct 2026, 13:34 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-r53p-7pc4-xj5r)

## Sources

- [GitHub Advisory Database: GHSA-r53p-7pc4-xj5r](https://github.com/advisories/GHSA-r53p-7pc4-xj5r)
- [OSV: GHSA-r53p-7pc4-xj5r](https://osv.dev/vulnerability/GHSA-r53p-7pc4-xj5r)
- <https://github.com/nodejs/undici/security/advisories/GHSA-r53p-7pc4-xj5r>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-18540>
- <https://github.com/nodejs/undici/commit/0160a719063fb0a77f4fdf9500b9166b91e14329>
- <https://github.com/nodejs/undici/commit/cd8af90b38ae33c2838d54a2d629774122effe95>
- <https://github.com/nodejs/undici/commit/ce31bc824b578008faae5d3350da66c1b5f71548>
- <https://hackerone.com/reports/3900104>
- <https://hackerone.com/reports/3900615>
- <https://cna.openjsf.org/security-advisories.html>
- <https://github.com/nodejs/undici>
- <https://github.com/nodejs/undici/releases/tag/v6.28.1>
- <https://github.com/nodejs/undici/releases/tag/v7.29.1>
- <https://github.com/nodejs/undici/releases/tag/v8.10.2>

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-r53p-7pc4-xj5r>, 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-r53p-7pc4-xj5r/>. Everything for agents: <https://agentprime.io/llms.txt>.