# Phoenix.HTML vulnerable to attribute injection via unvalidated attribute names in attributes_escape/1

Advisory record · `EEF-CVE-2026-117645`

- **Identifiers:** `EEF-CVE-2026-117645` · `CVE-2026-117645`
- **State:** Confirmed
- **Severity:** CVSS 5.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-79](https://cwe.mitre.org/data/definitions/79.html)
- **Tags:** [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md)
- **Published:** 30 Oct 2026
- **Updated:** 30 Oct 2026
- **Reviewed by a person:** No

Published by OSV at 30 Oct 2026, 20:25 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `phoenix_html` (Hex): affected `>=1.0.0, <3.3.5 || >=4.0.0, <4.4.0`; fixed in `3.3.5`, `4.4.0`

## 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

- 5.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`, from CNA (EEF)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0032, the 24th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 30 Oct 2026, 21:16 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-117645)
- 31 Oct 2026, 15:25 UTC: First seen by agentprime
- 31 Oct 2026, 15:25 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/EEF-CVE-2026-117645)

## Sources

- [OSV: EEF-CVE-2026-117645](https://osv.dev/vulnerability/EEF-CVE-2026-117645)
- <https://cna.erlef.org/cves/CVE-2026-117645.html>
- <https://github.com/phoenixframework/phoenix_html/commit/6ad3a1d7960891a468d54636054a98e11dfb5111>
- <https://github.com/phoenixframework/phoenix_html/commit/d9e4e6b2d9be49e25fb6d6b4fdbb2008174f01a6>
- <https://github.com/phoenixframework/phoenix_html/commit/a47dc8944a773b7e9273d9691dc6744ec793f1de>
- <https://hex.pm/packages/phoenix_html>

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/EEF-CVE-2026-117645>, 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/EEF-CVE-2026-117645/>. Everything for agents: <https://agentprime.io/llms.txt>.