check-jsonschema default caching for remote schemas allows for cache confusionGHSA-q6mv-284r-mp36
HIGHFix: python-jsonschema/check-jsonschema@c52714bGHSA-q6mv-284r-mp36 is a high-severity (CVSS 7.1) CWE-349 vulnerability in check-jsonschema. A fix is available for check-jsonschema — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-q6mv-284r-mp36.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
check-jsonschemaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
check-jsonschema is a CLI and set of pre-commit hooks for jsonschema validation. 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. This issue has been patched in version 0.30.0. All users are advised to upgrade. A few workarounds exist: 1. Users can use --no-cache to disable caching. 2. 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.) 3. 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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | check-jsonschema | all versions | 0.30.0pip install --upgrade 'check-jsonschema==0.30.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for check-jsonschema, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update check-jsonschema to 0.30.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-q6mv-284r-mp36 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is of significant severity because it directly undermines the integrity of the JSON schema validation process, a important mechanism for ensuring data consistency and security in many applications. By exploiting the cache naming collision, an attacker can inject a malicious schema that bypasses…
- 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.jsonSource: Red Hat security advisory for GHSA-q6mv-284r-mp36 (CC BY 4.0)
Frequently Asked Questions
Is GHSA-q6mv-284r-mp36 in your dependencies?
Find it across PyPI, including transitive dependencies.