# iCalendar has ICS injection via unsanitized URI property values

Advisory record · `GHSA-pv9c-9mfh-hvxq`

- **Identifiers:** `GHSA-pv9c-9mfh-hvxq` · `CVE-2026-33635`
- **State:** Confirmed
- **Severity:** CVSS 4.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-93](https://cwe.mitre.org/data/definitions/93.html)
- **Tags:** [Other injection](https://agentprime.io/advisories/tag/injection.md)
- **Published:** 24 Mar 2026
- **Updated:** 27 Mar 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 24 Mar 2026, 19:13 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `icalendar` (RubyGems): affected `>=2.0.0, <2.12.2`; fixed in `2.12.2`

## 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

- 4.3 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0025, the 17th 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 24 Mar 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-pv9c-9mfh-hvxq](https://github.com/advisories/GHSA-pv9c-9mfh-hvxq)
- [OSV: GHSA-pv9c-9mfh-hvxq](https://osv.dev/vulnerability/GHSA-pv9c-9mfh-hvxq)
- <https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-33635>
- <https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265>
- <https://github.com/icalendar/icalendar>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml>

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-pv9c-9mfh-hvxq>, 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-pv9c-9mfh-hvxq/>. Everything for agents: <https://agentprime.io/llms.txt>.