# REXML round-trip instability

Advisory record · `GHSA-8cr8-4vfw-mr7h`

- **Identifiers:** `GHSA-8cr8-4vfw-mr7h` · `BIT-ruby-2021-28965` · `BIT-ruby-min-2021-28965` · `CVE-2021-28965`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-115](https://cwe.mitre.org/data/definitions/115.html) · [CWE-611](https://cwe.mitre.org/data/definitions/611.html)
- **Tags:** [XML external entities (XXE)](https://agentprime.io/advisories/tag/xxe.md) · [CWE-115](https://agentprime.io/advisories/tag/cwe-115.md)
- **Published:** 30 Apr 2021
- **Updated:** 27 Jan 2025
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 30 Apr 2021, 17:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `rexml` (RubyGems): affected `<3.2.5`; fixed in `3.2.5`

## 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

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.051, the 92nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 30 Apr 2021. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-8cr8-4vfw-mr7h](https://github.com/advisories/GHSA-8cr8-4vfw-mr7h)
- [OSV: GHSA-8cr8-4vfw-mr7h](https://osv.dev/vulnerability/GHSA-8cr8-4vfw-mr7h)
- <https://nvd.nist.gov/vuln/detail/CVE-2021-28965>
- <https://github.com/ruby/rexml/commit/2fe62e29094d95921d7e19abbd2e26b23d78dc5b>
- <https://github.com/ruby/rexml/commit/3c137eb119550874b2b3e27d12b733ca67033377>
- <https://github.com/ruby/rexml/commit/6a250d2cd1194c2be72becbdd9c3e770aa16e752>
- <https://github.com/ruby/rexml/commit/9b311e59ae05749e082eb6bbefa1cb620d1a786e>
- <https://github.com/ruby/rexml/commit/a659c63e37414506dfb0d4655e031bb7a2e73fc8>
- <https://github.com/ruby/rexml/commit/f7bab8937513b1403cea5aff874cbf32fd5e8551>
- <https://github.com/ruby/rexml/commit/f9d88e4948b4a43294c25dc0edb16815bd9d8618>
- <https://hackerone.com/reports/1104077>
- <https://github.com/ruby/rexml>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rexml/CVE-2021-28965.yml>
- <https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WTVFTLFVCSUE5CXHINJEUCKSHU4SWDMT>

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-8cr8-4vfw-mr7h>, 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-8cr8-4vfw-mr7h/>. Everything for agents: <https://agentprime.io/llms.txt>.