# Cookie attribute injection in Plug.Conn.Cookies.encode/2

Advisory record · `GHSA-wpmj-jh88-rpgm`

- **Identifiers:** `GHSA-wpmj-jh88-rpgm` · `CVE-2026-56813` · `EEF-CVE-2026-56813`
- **State:** Confirmed
- **Severity:** CVSS 2.1 Low
- **Critical:** No
- **Weakness (CWE):** [CWE-141](https://cwe.mitre.org/data/definitions/141.html)
- **Tags:** [CWE-141](https://agentprime.io/advisories/tag/cwe-141.md)
- **Published:** 10 Jul 2026
- **Updated:** 24 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 10 Jul 2026, 12:51 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `plug` (Hex): affected `>=0.1.0, <1.16.6 || >=1.17.0, <1.17.4 || >=1.18.0, <1.18.5 || >=1.19.1, <1.19.5 || >=1.20.0, <1.20.3`; fixed in `1.16.6`, `1.17.4`, `1.18.5`, `1.19.5`, `1.20.3`

## 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0022, the 12th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 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-2026-56813)

## Sources

- [GitHub Advisory Database: GHSA-wpmj-jh88-rpgm](https://github.com/advisories/GHSA-wpmj-jh88-rpgm)
- [OSV: GHSA-wpmj-jh88-rpgm](https://osv.dev/vulnerability/GHSA-wpmj-jh88-rpgm)
- <https://github.com/elixir-plug/plug/security/advisories/GHSA-wpmj-jh88-rpgm>
- <https://cna.erlef.org/cves/CVE-2026-56813.html>
- <https://github.com/elixir-plug/plug/commit/f26876aa67aaeb38e616638aa3efbcc2fe2906a5>
- <https://github.com/elixir-plug/plug/commit/3f00dfad4e20ba88472e315c90a25742bf178f8e>
- <https://github.com/elixir-plug/plug/commit/a6d1248659022749869963fd302687165ecf8c8b>
- <https://github.com/elixir-plug/plug/commit/4167981747fe9ce75f374b94a28861ae950ea992>
- <https://github.com/elixir-plug/plug/commit/149d9ed68fee0b4f77efd1e835ce5d785856697b>
- <https://github.com/elixir-plug/plug/commit/eceb8315ce9a31ef784943a95a8624ebd1bc7e06>
- <https://hex.pm/packages/plug>

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-wpmj-jh88-rpgm>, 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-wpmj-jh88-rpgm/>. Everything for agents: <https://agentprime.io/llms.txt>.