CVE-2026-55875 Helium: SSRF via External Calendar URL Allows Authenticated Users to Probe Internal Network
Authenticated users can trigger server-side requests to internal hosts via external calendar URLs, enabling network reconnaissance and potential access to internal services.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55875?
CVE-2026-55875 is a medium-severity server-side request forgery vulnerability in HeliumEdu platform, published on 15 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-918
Which versions are affected by CVE-2026-55875?
How do I fix CVE-2026-55875?
No fix has been published for CVE-2026-55875 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-55875 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55875 exists.
Sources
Also known as GHSA-2f83-94pv-v3f5.