CVE-2026-55876: Helium: Stored XSS via Unrestricted SVG File Upload, Authenticated Users Can Store Executable Scripts
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-04 15:41 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
Helium is a free online student planner for classes, homework, grades, and notes. Prior to 2.2.60, the POST /planner/attachments/ endpoint allows authenticated users to upload SVG and HTML attachments because conf/configs/common.py omits those formats from BLOCKED_ATTACHMENT_EXTENSIONS and BLOCKED_ATTACHMENT_MIME_TYPES, and helium/planner/serializers/attachmentserializer.py relies on those blocklists. An uploaded SVG served as image/svg+xml can execute embedded script when a visitor opens its public attachment URL, allowing persistent attacker-controlled active content and phishing under an application-managed storage URL. The attachment storage uses a separate origin from the application, so same-origin policy prevents the script from reading application cookies or storage, and application-session compromise is not supported by the maintained deployment configuration. This issue is fixed in version 2.2.60.
Description quoted from the CVE record (assigned by GitHub_M, published 2026-10-15).
Weakness: CWE-79: Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’)
How it can be exploited
Exploitable over the network with low attack complexity needing low privileges and a user must take an action. Impact: confidentiality none, integrity low, availability none. CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: no. Technical impact: partial.
Public exploit evidence (Exploit Observer)
Exploit Observer found 3 code repositories naming this CVE.
Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.
See all 5 references on Exploit Observer
Live scores
- EPSS
- 0.002
low predicted chance of attack - VEDAS
- 0.988
strong exploit evidence - On CISA KEV
- Not listed
- Detection rule
- Suricata
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| HeliumEdu platform | version < 2.2.60 | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.
How to detect it
Suricata rules (network detection)
1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-55876 Helium - SVG Attachment Stored XSS Upload. Add them to your Suricata rule set and reload.
Show the rules
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-55876 Helium - SVG Attachment Stored XSS Upload"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/planner/attachments"; nocase; fast_pattern; http.request_body; content:"image/svg+xml"; nocase; classtype:web-application-attack; reference:cve,CVE-2026-55876; reference:url,https://www.exploit.observer/?keyword=CVE-2026-55876&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=helium&match=exact; sid:1084405; rev:1;)
CVE-2026-55876.rules on GitHub
References
Other references
- https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c (x_refsource_CONFIRM)
- https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88 (x_refsource_MISC)
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.
Supporting partners
