Classroom 50 is a free and open-source tool for managing and grading programming assignments via GitHub. Prior to version 1.11.0, `gh teacher download` clones each student's assignment repository and then writes autograde artifacts (`result.json` and `results.json`) into the just-cloned working tree. The write followed symlinks, so a student who committed `result.json` or `results.json` as a **symlink** (materialized verbatim by `git clone`) could redirect the teacher's write to an arbitrary path — e.g. `~/.zshrc`, `~/.ssh/authorized_keys`, a cron file, or an in-clone `.git/hooks/*` file that git subsequently executes. The written bytes are attacker-controlled (the student's uploaded release asset for `result.json`; student-chosen submit-tag names for `results.json`). This is an arbitrary file write leading to code execution as the teacher, whose `gh` token carries `admin:org`, `repo`, and `workflow` across the entire classroom organization. Version 1.11.0 contains a patch. Some workarounds are available. Avoid running `gh teacher download` against untrusted student repositories, or run it inside a disposable sandbox / container with no access to sensitive host files or credentials. Inspect cloned trees for symlinked, hardlinked, or special (`result.json`/`results.json`) entries before allowing the artifact-refresh step to run.
| Métrique | Valeur | Interprétation |
|---|---|---|
|
AV (Vecteur d'Attaque)
Attack Vector
|
Network (N)
|
Exploit possible à distance via réseau (HTTP, API, etc.) |
|
AC (Complexité d'Attaque)
Attack Complexity
|
Low (L)
|
Peu de conditions requises pour exploiter |
|
PR (Privilèges Requis)
Privileges Required
|
None (N)
|
Aucune authentification requise |
|
UI (Interaction Utilisateur)
User Interaction
|
Unknown (P)
|
Interaction inconnue |
|
S (Périmètre)
Scope
|
Unchanged (U)
|
Impact reste dans le périmètre du composant compromis |
|
C (Impact Confidentialité)
Confidentiality Impact
|
High (H)
|
Divulgation totale d'informations |
|
I (Impact Intégrité)
Integrity Impact
|
High (H)
|
Modification totale des données possible |
|
A (Impact Disponibilité)
Availability Impact
|
High (H)
|
Interruption totale du service possible |
Classroom 50 vulnerable to arbitrary file overwrite on the teacher's machine via symlink in a student repo (gh teacher download)