GHSA-q6mv-284r-mp36
check-jsonschema default caching for remote schemas allows for cache confusion
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| PyPI | check-jsonschema | < 0.30.0 | 0.30.0 |
Details
As written in the advisory (Markdown source, shown as plain text).
### Impact
The default cache strategy uses the basename of a remote schema as the name of the file in the cache, e.g. `https://example.org/schema.json` will be stored as `schema.json`. This naming allows for conflicts. If an attacker can get a user to run `check-jsonschema` against a malicious schema URL, e.g., `https://example.evil.org/schema.json`, they can insert their own schema into the cache and it will be picked up and used instead of the appropriate schema.
Such a cache confusion attack could be used to allow data to pass validation which should have been rejected.
### Patches
A patch is in progress but has not yet been released.
### Workarounds
- Users can use `--no-cache` to disable caching.
- Users can use `--cache-filename` to select filenames for use in the cache, or to ensure that other usages do not overwrite the cached schema. (Note: this flag is being deprecated as part of the remediation effort.)
- Users can explicitly download the schema before use as a local file, as in `curl -LOs https://example.org/schema.json; check-jsonschema --schemafile ./schema.json`
References
External links from the advisory. They lead to third-party sites.