GHSA-c4cm-r9fh-jgj9 — commonground-api-common
Fix: maykinmedia/commonground-api-common@20d9345GHSA-c4cm-r9fh-jgj9 is a security vulnerability in commonground-api-common. No vendor fix is recorded yet; mitigation options are listed below.
commonground-api-common unexploitable privilege escalation in JWT authentication middleware
Real-World Exposure
commonground-api-common🐍vng-api-common🐍vng-api-common-utrechtReal-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
Impact
This is a privilege escalation vulnerability. The impact is negligible and entirely theoretical.
A non-exploitable weakness was found in how the client-supplied JWTs are verified. Because an explicit allow-list of known algorithms is used in the PyJWT library, user-supplied (invalid) algorithms are rejected.
If this was not the case, then the client JWTs could be tampered with, resulting in privilege escalation which would allow the attacker to perform any operation as any client (impersonation) without leaving a trace of the real user/client.
Patches
Will be fixed in 1.12.2
Workarounds
None needed. But be careful when updating PyJWT. Check that the used PyJWT has no algorithms specified with a name in "", "HS25", "HS2", "HS", "H", or that those algorithms are acceptable.
Details
The header and payload of JSON Web Tokens (JWTs) are cryptographically signed with an algorithm. A JWT has a header field alg that specifies the algorithm used in the signature.
The vng-api-common.middleware.AuthMiddleware uses PyJWT to check the validity of JWT and indicates it should be "HS256", otherwise an attacker could construct a token with a cryptographically weak token. It should indicate this with a list of acceptable algorithms ["HS256"], but instead the string "HS256" is passed to PyJWT. PyJWT does not check the type of the argument and checks if the alg string in the header exists in the acceptable algorithms value with the in operator. Any substring of "HS256" passes this in check. It is not exploitable because there is no such substring in de set of algorithms PyJWT supports.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | commonground-api-common | all versions | No fix |
| 🐍PyPI | vng-api-common | all versions | No fix |
| 🐍PyPI | vng-api-common-utrecht | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for commonground-api-common, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of commonground-api-common has shipped for GHSA-c4cm-r9fh-jgj9 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-c4cm-r9fh-jgj9 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-c4cm-r9fh-jgj9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-c4cm-r9fh-jgj9 in your dependencies?
O3 Security finds GHSA-c4cm-r9fh-jgj9 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.