webmedium

RevengeNinja

hackerlab

Task: a FastAPI preview endpoint rendered attacker-controlled Jinja2 templates inside SandboxedEnvironment with a live Pydantic user object in context. Solution: abuse exposed BaseModel.parse_raw(..., content_type=\"application/pickle\", allow_pickle=True) to deserialize a malicious pickle, gain RCE, and read the flag file.

$ ls tags/ techniques/
rcesstisandbox_escapefastapijinja2pickleinsecure_deserializationpydantic
ssti_jinja2sandbox_bypass_via_exposed_object_methodspickle_deserialization_rcefile_write_rce
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