# Undertow is Vulnerable to HTTP Request/Response Smuggling Advisory record · `GHSA-3gv6-g396-9v4r` - **Identifiers:** `GHSA-3gv6-g396-9v4r` · `CVE-2026-28367` - **State:** Confirmed - **Severity:** CVSS 8.7 High - **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:** 27 Mar 2026 - **Updated:** 4 Nov 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 27 Mar 2026, 18:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `io.undertow:undertow-core` (Maven): affected `>=2.3.0.Final, <2.3.25.Final || <2.2.40.Final`; fixed in `2.3.25.Final`, `2.2.40.Final` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Undertow (io.undertow:undertow-parent) versions up to and including 2.3.23.Final are vulnerable to HTTP request smuggling. A remote attacker can send a crafted header block terminator that some proxy servers interpret differently, which can lead to unauthorized access or manipulation of web requests. No fixed version is listed. Written 2 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 - 8.7 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N`, from CNA (redhat) - **CISA KEV:** Not listed. - **EPSS:** 0.0072, the 54th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 27 Mar 2026, 16:13 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-28367) - 27 Mar 2026, 17:16 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-28367) - 27 Mar 2026, 18:31 UTC: [Confirmed by GitHub Advisory Database](https://github.com/advisories/GHSA-3gv6-g396-9v4r) - 31 Oct 2026, 14:17 UTC: First seen by agentprime - 31 Oct 2026, 14:17 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-3gv6-g396-9v4r) ## Sources - [GitHub Advisory Database: GHSA-3gv6-g396-9v4r](https://github.com/advisories/GHSA-3gv6-g396-9v4r) - [OSV: GHSA-3gv6-g396-9v4r](https://osv.dev/vulnerability/GHSA-3gv6-g396-9v4r) - - - - - - - - - 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 (), 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: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .