GHSA-5hcj-rwm6-xmw4
LOWbiscuit-java vulnerable to public key confusion in third party block
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.biscuitsec:biscuitReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Tokens with third-party blocks containing trusted annotations generated through a third party block request. Due to implementation issues in biscuit-java, third party block support in published versions is inoperating. Nevertheless, to synchronize with other implementations, we publish this advisory and the related fix.
Description
Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it:
the public key of the previous block (used in the signature) the public keys part of the token symbol table (for public key interning in datalog expressions) A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair.
Consider the following example (nominal case)
- Authority A emits the following token:
check if thirdparty("b") trusting ${pubkeyB} - The well-behaving holder then generates a third-party block request based on the token and sends it to third-party authority B
- Third-party B generates the following third-party block
thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC} - The token holder now must obtain a third-party block from third party C to be able to use the token
Now, with a malicious user:
- Authority A emits the following token:
check if thirdparty("b") trusting ${pubkeyB} - The holder then attenuates the token with the following third party block
thirdparty("c"), signed with a keypair pubkeyD, privkeyD) they generate - The holder then generates a third-party block request based on this token, but alter the
ThirdPartyBlockRequestpublicKeys field and replace pubkeyD with pubkeyC - Third-party B generates the following third-party block
thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC} - Due to the altered symbol table, the actual meaning of the block is
thirdparty("b"); check if thirdparty("c") trusting ${pubkeyD} - The attacker can now use the token without obtaining a third-party block from C.
Patches
Has the problem been patched? What versions should users upgrade to?
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
References
Are there any links users can visit to find out more?
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.biscuitsec:biscuit | ≥ 3.0.0&&< 4.0.0 | 4.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.biscuitsec:biscuit. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.biscuitsec:biscuit to 4.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5hcj-rwm6-xmw4 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.
How O3 protects you
O3 pinpoints whether GHSA-5hcj-rwm6-xmw4 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-5hcj-rwm6-xmw4. 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-5hcj-rwm6-xmw4 in your dependencies?
O3 detects GHSA-5hcj-rwm6-xmw4 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.